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SAPPMA Technical Manual 2011

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Page 1: SAPPMA Technical Manual 2011

1SAPPMA TECHNICAL MANUAL | jANUAry 2011 | 3rd Edition

SOUTHERN AFRICAN PLASTIC PIPEMANUFACTURERS ASSOCIATION

Copyright Protected

Page 2: SAPPMA Technical Manual 2011

INTRODUCTION BY THE CEO OF SAPPMA

You are now reading the third edition of the SAPPMA Technical Pipe Manual. Since the fi rst edition saw the light in 2006, we have continually updated, amended and added to the publication. This edition now includes for the fi rst time, sections on Hot & Cold Water Plumbing Pipe, HDPE fabricated fi ttings, as well as the jointing of HDPE.

An enormous amount of data could be included in a manual such as this, but for practical and fi nancial reasons we limit it to the most important/relevant info required by a design engineer. I therefore repeat the standing invitation to users of this book, to send us your constructive comments for future improvements.

Pipelines are one of the three most important elements of a country’s infrastructure. The disruption of water supply and sewage disposal is a most unpleasant experience - something that could be avoided by reliable piping systems. The key elements in achieving reliability are:

o Knowledgeable civil engineering design (hydraulics, soil conditions)

o Selection of the right pipe material (plastic, steel, concrete, etc.) for the application

o Using the best available pipe grade polymer

o Pipe manufacturing of the highest standard in approved factories

o Installation by skilled and responsible contractors

When done correctly, there is no reason why plastic pipelines should not give reliable service for a hundred years or more!

We trust this manual will enable you to make informed choices in terms of the above and that your experiences with the plastics pipe industry will always be pleasant and constructive.

Jan Venter (Pr Eng)

SAPPMA’s role

The role and importance of SAPPMA can hardly be overestimated. With big and ever increasing demand for water and sewage systems, a serious shortage of water in the country and the need for reliable, leak-free, long term piping systems, the critical importance of products of the highest quality is a clear. This is an area where SAPPMA plays a key role, together with the SABS.

The natural tendency of people is to follow the way of least resistance; this is evident in all areas of society. In the piping industry, it is far easier and a lot more profi table to use the cheapest raw material available and to overlook some critical long test requirements. Experience has shown that even the SABS mark on the product is not necessarily a watertight guarantee.

SAPPMA continuously introduce additional measures to its members over and abovethe requirements of the national standards. Members are also subjected to regular factory audits. It is a matter of pride to use the SAPPMA logo on your products.

Purpose

Our purpose is to create absolute consumer confi dence within the Plastic Pipe Industry and to ensure the long term health & sustainability of high quality plastic pipes and pipe systems.

INTRODUCTION

SAPPMA TECHNICAL MANUAL | jANUAry 2011 | 3rd Edition

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PART I GENERAL ............................................................................................................. 3

INTRODUCTION .............................................................................................................. 4 Purpose and Scope of Manual ......................................................................................... 4 Plastic Pipe Applications ............................................................................................... 4 Pipe Material Properties ............................................................................................... 4 International Market .................................................................................................... 6 South African Market ................................................................................................... 6 Pipeline Design and Selection ......................................................................................... 8 Gravity and Pressure Systems ......................................................................................... 8

PIPE MATERIAL CLASSIFICATION ......................................................................................... 10 Soil Structure Systems ................................................................................................. 10 Flexible and Rigid Pipes ............................................................................................... 11 Classifi cation of Plastics .............................................................................................. 13 Comparison of Various Flexible Pipes ............................................................................... 13 Regression Curves (stress/time relationship) ...................................................................... 15

PART II SELECTION AND INSTALLATION .................................................................................. 19

HYDRAULIC REQUIREMENTS............................................................................................... 20 Basic Principles ......................................................................................................... 20 Operating Pressure, Hoop Stress and Wall Thickness ............................................................. 23

Surge and Fatigue ...................................................................................................... 24 Factory Tests ............................................................................................................ 25

EXTERNAL LOADS ........................................................................................................... 26 Design Basis ............................................................................................................. 26 Load Classifi cation ..................................................................................................... 26

Pipe Stiffness ........................................................................................................... 27 Determining Required Pipe Stiffness ................................................................................ 28

Vertical Defl ection ..................................................................................................... 30

DURABILITY REQUIREMENTS .............................................................................................. 31 Durability ................................................................................................................ 31

SYSTEM COMPONENTS ..................................................................................................... 31 Secondary loads ........................................................................................................ 31 Manholes ................................................................................................................ 31 Joints And Fittings ..................................................................................................... 31 Valves .................................................................................................................... 32

INSTALLATION ............................................................................................................... 32 Preconstruction Activities............................................................................................. 32 Excavation .............................................................................................................. 32 Embedment ............................................................................................................. 33 Pipe Laying and Jointing .............................................................................................. 33 Backfi lling ............................................................................................................... 34 Anchoring ................................................................................................................ 35 Site Tests ................................................................................................................ 35

TABLE OF CONTENTS

SAPPMA TECHNICAL MANUAL | jANUAry 2011 | 3rd Edition 1

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PART III PLASTIC PIPE PROPERTIES ....................................................................................... 37

POLYETHYLENE (PE) ....................................................................................................... 38 Typical Physical Properties ........................................................................................... 38 Benefi ts of PE ............................................................................................................38 Polymers ................................................................................................................. 38

Applications ............................................................................................................. 39 Benefi ts of PE 100 ...................................................................................................... 40 Design .................................................................................................................... 40 Other Relevant Values ................................................................................................. 44 PE in Gas Distribution ................................................................................................. 44 Cost Benefi ts of PE ..................................................................................................... 45 Pipe Dimensions ........................................................................................................ 45 POLYVINYL CHLORIDE (PVC) .............................................................................................. 50 Composition of PVC Pipe material ................................................................................... 50 Physical Properties ......................................................................................................50

Benefi ts of PVC ......................................................................................................... 51 Applications of PVC Pipe Systems ....................................................................................52 Design .....................................................................................................................52 Pipe Dimensions .........................................................................................................55 Strength and Toughness ............................................................................................... 62 Effect of Temperature Change ....................................................................................... 63

POLYPROPYLENE (PP) ...................................................................................................... 65 Benefi ts and Specifi cations ............................................................................................65

POLYETHYLENE JOINTING SYSTEMS ......................................................................................66 Polyethylene Welding Processes ......................................................................................66

Heated - Tool Socket Welding .........................................................................................68 Welder Training and Qualifi cations ...................................................................................71 Welding Equipment .....................................................................................................72 Destructive Test .........................................................................................................72 Air Test ....................................................................................................................73 Hydraulic Pressure Test ................................................................................................73 Minimal Dimensional Requirements for Fittings ....................................................................74 Fabricated Fittings (HDPE & PP) ..................................................................................... 76 Segmented Bends ...................................................................................................... 79 Seamless Long Radius Bends Plain Ended .......................................................................... 80 Electrofusion Socket Dimensions .................................................................................... 81 Spigot Dimensions ...................................................................................................... 82

HOT & COLD WATER PRESSURE PIPES ................................................................................... 83 Introduction .............................................................................................................83 Classifi cation ............................................................................................................ 84

APPENDICES ..................................................................................................................87 Appendix A: Identifi cation of Plastics ................................................................................87 Appendix B: Chemical Resistance of Thermoplastics used for pipes ............................................88

ABOUT SAPPMA ........................................................................................................... 100

2 SAPPMA TECHNICAL MANUAL | jANUAry 2011 | 3rd Edition

TABLE OF CONTENTS

Page 5: SAPPMA Technical Manual 2011

PART I GENERAL ............................................................................................................. 3

INTRODUCTION .............................................................................................................. 4

Purpose and Scope of Manual ......................................................................................... 4

Plastic Pipe Applications ............................................................................................... 4

Pipe Material Properties ............................................................................................... 4

International Market .................................................................................................... 6

South African Market ................................................................................................... 6

Pipeline Design and Selection ......................................................................................... 8

Gravity and Pressure Systems ......................................................................................... 8

PIPE MATERIAL CLASSIFICATION ......................................................................................... 10

Soil Structure Systems ................................................................................................. 10

Flexible and Rigid Pipes ............................................................................................... 11

Classifi cation of Plastics .............................................................................................. 13

Comparison of Various Flexible Pipes ............................................................................... 13

Regression Curves (stress/time relationship) ...................................................................... 15

3SAPPMA TECHNICAL MANUAL | jANUAry 2011 | 3rd Edition

PART 1 GENERAL

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SAPPMA TECHNICAL MANUAL | jANUAry 2011 | 3rd Edition4

Purpose and Scope of Manual

The behaviour of plastic pipes used for buried pipelines has been researched and studied for many years. There is however, in general, a lack of technical understanding amongst designers, specifi ers and users of plastic pipes and fi ttings about these products. This lack of understanding relates specifi cally to the differences between the various types of plastic pipes and how the principles developed should be applied to ensure that these products provide a long trouble free service life.

The purpose of this manual is to provide the basic information and guidance needed to ensure that plastic pipes for water supply and waste-water disposal applications are correctly selected and specifi ed. This publication does not attempt to replace published text books and codes on the subject, but is a basic guide to the use, selection and specifi cation of these products. It covers the differences between the various types of plastic pipe and the basic procedures for determining product size, strength and material properties for a range of applications.

It has been written from the perspective of the civil or municipal designer who probably has no formal education or training in the use of these products.

Plastic Pipe Applications

Plastic pipe is used throughout the entire spectrum of potential pipe applications, including:

• Water distribution and wastewater disposal

• Mining applications such as the conveyance of potable water, cooling, slurries and air

• Irrigation

• Plumbing(Hot and cold water)

• Effl uent conveyance in the chemical and other industries

• Telecommunications applications such as conduits for cables or fi bre optics

• Gas distribution

• Rehabilitation of deteriorated pipelines used in the above applications

Plastic pipes fall into two broad categories, namely thermoplastics such as PVC and PE and thermoset plastics such as GRP. Thermoplastics can tolerate high strains and can be recycled. Thermoset plastics can tolerate high stress and cannot be recycled. The current edition of this publication focuses on thermoplastics. A future revision will include sections on the thermoset plastics.

Pipe Material Properties

Like all materials there are positive and negative properties that need to be considered. Positive characteristics are:

• Resistance against chemicals, corrosion and abrasion

• Light weight and ease of handling

• Available in long lengths, reducing the number of joints

• Flexibility and toughness

• Excellent hydraulic properties with low friction resistance throughout life

• Able to withstand water hammer

• Very low thermal conductivity

There are also some characteristics that need special care in the design of pipelines:

• High coeffi cient of expansion/contraction with temperature changes compared to metallic pipe

• Flexibility requires shorter support distances when installed above ground

• Flammability (PVC is self-extinguishing and PE not)

By understanding these properties the designer can take them into account and take the necessary precautions.

INTRODUCTION

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TABLE 1: GENErAL PrOPErTIES OF THErMOPLASTICS

Property PE PP PVC

Surface feel Waxy Waxy Smooth

Usual colours Black Ivory white, blue, green brown

Blue, Sand, White

Sound when dropped Clatter Clatter High clatter

Combustibility Bright fl ame: Drops continue to burn while falling

Bright fl ame: Drops continue to burn while falling

Self Extinguishing

Odour of smoke after fl ame is extinguished

Like candles Like resin Pungent like hydrochloric acid

Nail test impression Impression possible Very slight impression possible

Impression not possible

Floats on water Yes Yes No

Notch sensitivity No No Yes (not in case of PVC-M & PVC-O)

Method of joining Thermal or mechanical welding and/or spigot or socket

Thermal or mechanical welding and/or spigot or socket

Solvent cement and/or thermal, chemical or mechanical welding and/or spigot or socket

Linear expansion mm/m/oC

0.2 0.15 0.07

Thermal conductivity- kcal/mhoC

0.40 0.19 0.10

Specifi c heat- kcal/mhoC

0.55 0.46 0.23

Specifi c weight- kg/m3

0.96 0.91 1.45

Tensile yield at 20oC- MPa (Short Term)

17-24 23-31 48-75

Young’s modulus at 20oC - MPa (Short Term)

800 - 1100 1250 - 1700 3000-4000

Note: The designer should check with the pipe supplier about the product and its properties.

INTRODUCTION

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International Market

Worldwide, the most popular plastic pipe materials are PVC (polyvinyl chloride), PE (polyethylene), PP (polypropylene), GRP (glass reinforced polyester), ABS (acrylonitrile butadiene styrene) and PB (polybutylene).

Plastics are a by-product of only ±4% of the world’s oil consumption. In exchange, plastics help conserve fossil fuels for power and heat. The increasing use of plastics in motor vehicles for instance, has led to decreases in overall mass and better fuel effi ciency. Europe, as an example, saves 12 million tons of oil per year in the automotive sector by using lightweight plastics. This is equivalent to 30 million tons of carbon dioxide each year.

Plastic pipes are used in many infrastructural and industrial applications such as water, gas and sewerage conveyance. In the European pipe market, plastic pipes rank fi rst among all pipe materials and globally about 54% of all pipes in terms of length installed are plastic. Plastic pipelines have encroached on steel and asbestos cement in traditional pressure systems and asbestos cement and concrete in the sewer market.

Old pipe installations in the developed world lose vast quantities of water, costing billions (11 million cubic meters of treated drinking water per day in the United States, with similar situations in Europe). The properties of certain types of plastic pipes are ideally suited to the rehabilitation of these deteriorated pipelines, promising continuous growth in plastic pipe use.

The continuous drive for competitive advantages in the piping industry has stimulated a great deal of research and development (R & D) by polymer scientists in the quest for higher performance at lower cost. Design stresses have increased from 10 to 32 MPa in PVC and 5 to 8 MPa in PE. Further developments can be expected, which will result in considerable reductions in wall thickness and product mass, as well as the ability to produce larger diameter pipes. The advancement of modern polymers has enabled the production of solid wall polyethylene (PE 100) pipe in diameters up to 2 500 mm with wall thicknesses

around 100 mm; structured wall pipe is made in even bigger sizes. In the US PVC pressure and sewer pipes are produced in diameters up to 1200 mm.

South African Market

The South African (SA) plastic pipe industry is well developed and compares very well with its counterparts in Europe and the US. The latest technology is used for processing and testing, polymers that comply with international standards. Several local companies are either subsidiaries of international fi rms, or are linked with technical licenses, thereby sharing in the benefi ts of the international research and development (R&D) and benchmarking against the best in the world.

The main source of the thermoplastic polymers is ethylene, obtained from either oil or coal. All have hydro-carbon molecular structures. PVC & LDPE polymers are locally produced by Sasol Polymers and HDPE by Safripol. The ethylene they both use as basic feedstock is obtained from Sasol Synfuels. A big pipeline recently completed from the Mozambique gas fi elds to Sasol in Secunda supplies natural gas as an additional source of feedstock. Some high performance polymers are imported.

Plastic pipes for various applications are made to SA national standards as detailed in Table 2. These standards are comparable to international standards and many are based on European documents.

INTRODUCTION

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TABLE 2: CUrrENT SOUTH AFrICAN PLASTIC PIPE rANGES AVAILABLE

Pipe Material & application

Nominal size

(mm)

Design Stress (MPa)

Pressure rating (bar)

Pipe Stiffness

(kPa)

Specifi cation Nominal StiffnesskN/m/m

PVC-U Rigid Pressure Pipe

20 - 500 10, 12.5 4 - 25 SANS 966:1

PVC-M Rigid Pressure Pipe

50 - 500 18 6 - 25 SANS 966:2

Mine Pipe 55 - 355 10 - 12.5 6 - 25 SANS 1283

PVC-O Rigid Pressure Pipe

110 - 250 28 9 - 16 SANS 1808 - 85

PVC Solid Wall Sewer Pipe

110 - 500 100, 300 SANS 791 2, 6

PVC Multilayer Sewer Pipe

110 - 250 100, 200, 400 SANS 1601 2, 4, 8

PVC –U. Corrugated pipe

110 - 250 400 SANS 1601 8

PE100 Pressure Pipe

16 -1000 8.0 6 - 20 SANS ISO 4427

PE80 Pressure Pipe

16 - 1000 6.3 3 - 20 SANS ISO 4427

PE100 Gas Pipe 16 - 630 5.0 10 SABS ISO 4437

PE Structured Wall Pipe

280 - 1800 200, 400, 800 ISO 9969 4, 8, 16

PE Corrugated Wall Pipe

75 - 160 400 ISO 9969 8

PP Pipe 8 - 1000 6.3 6 - 20 SANS 15494Parts 1,2,3 & 5

PP - R Hot & Cold pressure pipe

12 - 160 6.93 10 - 20 SANS 15874

PE - X Hot & Cold pressure pipe

7.6 10 - 20 SANS 15875

These standards are all performance specifi cations that prescribe the minimum requirements that the products must meet. They do not cover how the product should be selected or installed.

INTRODUCTION

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INTRODUCTION

Pipeline Design and Selection

The primary function of any pipeline is to convey a fl uid. It’s size is based on predictions of the future demand. It is usually not economic to design for the maximum predicted future fl ow. If a pipeline proves to be too small at some future date an additional pipeline can be constructed with minimal or no disruption to the operation of the existing one.

To meet this primary requirement the pipeline must also meet the secondary or supporting requirements of strength, water-tightness and durability. Usually it is in not meeting one of these secondary requirements that a pipeline fails. Irrespective of whether a pipeline is designed to serve a 20 year, 40 year or some other predicted population or demand it must be designed to meet the secondary requirements based on the worst case scenario. If it fails to meet these requirements, any remedial work will cause a major disruption to its operation and may necessitate its replacement even though it still has the required hydraulic capacity.

When there are junctions, transitions and changes in vertical or horizontal alignment access is generally needed. This takes the form of manholes or other appurtenant structures. In the case of pressure pipelines the accumulation of air in the system and the structures needed to house air relief valves or other devices also have to be considered. As these are vertical structures the loading on these is different from that on the adjacent sections of pipeline that are loaded with soil and as a result there can be relative movement between these structures and the adjacent pipes.

Many of the failures on pipelines occur at joints and in particular those at the interfaces with structures such as manholes. If the correct measures are not taken to minimize the disruption to fl ow through these structures and the associated energy losses not considered, the hydraulic performance of a pipeline can be seriously compromised. If measures are not taken to accommodate any potential relative movement between pipes and these structures, pipes can crack or deform resulting in leakages.

The structural design of buried pipelines involves the understanding of a complex system consisting of soil and traffi c loads, soil properties, water movement

through the soil and pipes and appurtenant structures made from a wide range of materials. The designer can do little about the installation conditions, but he can make decisions about the requirements the pipe must meet and then choose the most appropriate pipe material for the conditions on a particular project.

There are two broad categories of pipelines, namely pressure and gravity systems and the way in which they operate is very different. There are also two broad categories of pipe materials, namely rigid and fl exible and the way in which they respond to load is also very different. It is essential that the designer understands these two sets of differences.

Gravity and Pressure Systems

Pressure pipelines fl ow full and the energy in them has three components in addition to pipe diameter namely, velocity head, pressure head and frictional losses. With pressure pipelines it is the energy difference between the inlet and outlet that determines the discharge capacity. As the hydraulic performance of this type of pipeline is not dependant on its gradient the vertical alignment is essentially determined by the ground surface and it is placed at relatively shallow depths. The dominant stresses in the pipe wall will be those due to the internal pressure however the infl uence of external loads cannot be ignored.

Gravity pipelines on the other hand, especially stormwater drains and sewers that fl ow partly full, have no pressure component to their energy so they can fl ow down hill only. This means that gravity pipelines must be laid at gradients that will ensure self cleansing velocities for effi cient operation. With gravity pipelines it is the gradient of the fl attest section that will determine the capacity. To maintain self cleansing velocities it may be necessary to install such pipelines in deep trenches and at gradients that are not parallel to the ground surface. To achieve this they are frequently placed at depth below the surface. As a result the dominant stresses developed in the pipe wall are due to the external earth loads, although under certain circumstances internal pressure may also have to be considered. When pipes are used for low pressure or gravity applications it is the external loads that will determine the required wall thickness or pipe stiffness.

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INTRODUCTION

It needs to be appreciated that the way in which a pipe handles internal fl uid pressures and external earth loads is different. Internal pressure generates direct tension in the pipe wall, whereas external earth and traffi c loads are non symmetrical and cause circumferential bending of the pipe wall. In most soils the vertical loads will exceed the horizontal loads and the pipe deforms to form a horizontal ellipse. This effectively activates the lateral soil pressures resulting in the transfer of load to the surrounding soil.

Figure 1: Difference between gravity and pressure pipelines

(a) (b)

Where: hf - head loss due to friction (m) V - velocity (m/sec) g - acceleration due to gravity (m/sec2) hp - pressure head (m) D - pipe diameter (m) z - height above datum (m) Y - Depth of fl ow partially full pipe (m)

PRESSURE CONDUIT FLOWING FULL GRAVITY CONDUIT FLOWING PARTLY FULL

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Soil Structure Systems

The way in which the loads are carried will depend on the relative stiffness of the pipes and the surrounding soil. SANS 10102 part I (p18), uses the approach given in Young and Trott, namely:

Y = E’/SR (1) and SR = EI/D3 (2)Where Y - fl exural stiffness ratio, E’ - the soil stiffness SR - pipe ring stiffness E - elastic modulus for pipe material D - undeformed vertical diameter of pipe I - moment of inertia of section

This ratio ‘Y’ is directly proportional to soil stiffness and indirectly proportional to pipe ring stiffness, or fl exural stiffness as it is defi ned in this document. Soil stiffness can vary from 1 to 20 MPa. Pipe ring stiffnesses ranges from 1kN/m/m for fl exible pipes where the pipes deform and shed the load to the surrounding soil to >2 000kN/m/m for rigid pipes where the pipes carry the load directly by moment and shear. The ‘Y’ value of a rigid system is thus two to fi ve orders of magnitude less than that of a fl exible system. A comparison of the pipe materials commonly used in SA is shown in Figure 3.

-

Figure 2: Range of fl exural stiffness ratios for pipe materials used in South Africa

PIPE MATERIAL CLASSIFICATION

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As the fl exural stiffness ratio increases so the strength of the pipe/soil system becomes more dependant on the properties of the surrounding material. The emphasis shifts from ensuring that the pipe, produced in a factory has the required strength to carry the loads, to ensuring that the embedment around the pipe, constructed on site has the strength to provide the pipe with the required lateral support.

This fi gure also shows the difference between the various types of plastics, which the civil designer frequently does not appreciate. It should be appreciated that there is a signifi cant difference between the performance of the thermoplastics such as PE and PVC and the thermoset plastics such as GRP and GRE. This publication focuses on the former where the development of high strains will not cause the structural failure of the pipe wall. The same can not be said for GRP and GRE pipes where strain is a limiting factor. Excessive defl ection of PE or PVC pipe could however cause operational problems such as the water tightness of joints and accessibility for maintenance.

No matter what pipe material is used care must be taken to ensure that the foundation support is uniform.

Flexible and Rigid Pipes

Rigid pipes have to carry the imposed loads on their own and the critical structural parameter is their strength. The main determinant of these loads is usually the installation condition. On the other hand fl exible pipes defl ect under imposed loads and are reliant on the horizontal soil support that develops and the critical structural parameter is the soil stiffness around them. The main determinant of defl ection will be the stiffness of the surrounding material.

The standard installation conditions for rigid pipes are illustrated in Figure 3. A useful concept is the geostatic load, which is the load on the pipeline due to the prism of material directly over it. With a trench installation the loading will always be less than the geostatic loading because the frictional forces act upwards and reduce the loading on the pipe. With an embankment installation the loading will always be greater than the geostatic load because the frictional forces act downwards and increase the loading on the pipe.

Figure 3: Comparison of installation conditions for rigid pipes

TRENCH GEOSTATIC EMBANKMENT

PIPE MATERIAL CLASSIFICATION

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The geostatic load on a fl exible pipe will be the column of earth directly on top of it. The pipe will deform more under this load than the columns of earth on either side of it and as a result upward frictional forces will develop between the column of earth directly above the pipe and the columns of earth on either side of the pipe. The vertical load on the pipe will therefore be less than the prism load. Irrespective of the installation condition the load on a fl exible pipe will always be less than the geostatic load calculated by using its outside diameter.

The basic formula for calculating the soil load on a buried pipe is:

WE = CEγB2 (3)

Where WE - total earth load in kN/m of pipeline

CE - earth load coeffi cient

γ - fi ll material density

B - outside pipe diameter (BC) or trench width (BT)

For embankment installations the most severe loading on a rigid pipe occurs when the founding conditions are unyielding and the whole pipe projects above the

founding level. Once the fi ll height exceeds + 1.7BC there is a straight line relationship between load and fi ll height and there will be no limiting value to the load. These earth loads will be:

WE = 1.69γBc H in sand (4)

WE = 1.54γBc H in clay (5)

For trench installations upper limits to loading on a rigid pipe occur when complete arching action occurs.

WE = 2.63γBt2 in sand (6)

WE = 3.84γBt2 in clay (7)

In practice the walls of a trench dug through a sandy material will not stand and the equation (5) is hypothetical. Open trench installations are seldom so deep that full arching action and limiting loads can be achieved and hence it would be uneconomic to use these values to determine the required pipe strength.

A comparison of the loading on rigid and fl exible pipes under trench installation conditions is given in Figure 4.

Figure 4: Comparison of rigid and fl exible pipe in a trench installation

RIGID GEOSTATIC FLEXIBLE

PIPE MATERIAL CLASSIFICATION

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As the thermoplastic pipes such as those made from PVC, PE and PP have a high strain tolerance, they will deform more than the columns of earth next to them and the frictional forces that develop between the columns of earth will act upwards and reduce the load on the pipe. If the fi ll height is great enough full arching will take place and the earth load will have an upper limit as given by formulae (6) and (7) above where the trench width is replaced by the outside diameter of the pipe. This approach, however, is seldom taken.

PVC, PE & PP pipe have a proven track record of over 40 years.In the absence of details of actual soil properties and installation conditions the earth loads on fl exible pipes can conservatively be taken as:

WE = γBc H (8)

Where the terms are as defi ned above.

Classifi cation of Plastics

Plastics cover a wide range of synthetic materials which can be molded or formed when soft and set. They fall into two broad categories, thermoplastics and thermosets.

Thermoplastics soften when heated and harden when cooled. This cycle can be repeated over and over again.

Thermosets on the other hand are materials that when processed and shaped are hardened by heating. They cannot be softened again by further heating.

An international system for identifying plastics that uses a polymer identifying logo has been developed. This is given in Appendix A. Only some of these materials are used to manufacture pipes.

Comparison of Various Flexible Pipes

There are signifi cant differences between plastic pipes and steel pipes both in terms of their properties and applications. Some of the differences between PE, PVC and steel are listed in Table 3.

PIPE MATERIAL CLASSIFICATION

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TABLE 3: COMPArISON OF VArIOUS FLEXIBLE PIPES

PE PVC Steel

Flexibility

• Less affected by soil settlement

• Can be wound onto drums in diameters [Up to 160 mm in SA]

• Suitable for relining and ploughing in

• Cold bending radius at 20°C = 30D

• Suitable for temperatures down to minus 40°C

• Can withstand crushing

• Affected to some extent by soil settlement

• Only corrugated pipes can be wound onto drums (single wall)

• Limited use for relining

• Cold bending not possible

• Laying at sub-zero temperatures risky for PVC-U, less so for PVC-M and PVC-O

• PVC-U cannot withstand crushing, PVC-M can withstand to some extent and PVC-O can withstand crushing

• Affected to some extent by soil settlement

• Cannot be wound onto drums

• Diffi cult to use for relining pipe

• A limited amount of bending is possible

jointing Technique

• Can be fusion welded

• Joints have good tensile strength

• Special equipment required

• Bonded joints with good tensile strength. Can be bonded without costly special equipment

• Push-in joints easily made

• Victaulic restrained joints

• Can be welded

• Joints have good tensile strength

Chemical resistance

• Resistant to acids, alkalis, solvents, alcohol

• Not resistant to oxidizing acids, ketones, aromatic hydrocarbons and chlorinated hydrocarbons

• Resistant to microbial corrosion

• Resistant to all natural gas constituents

• Resistant to acids, alkalis, salt solutions and many organic compounds such as fats, oils, aliphatic hydrocarbons.

• Resistant to microbial corrosion

• Resistant to natural gas

• Limited resistance to chemicals

• Unsuitable for concentrated oxidizing acids

• Not resistant to microbial corrosion

• Not resistant to acid containing condensates (corrosion)

PIPE MATERIAL CLASSIFICATION

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PE PVC Steel

Weather resistance

• Due to the required carbon black additive, outdoor weathering has virtually no effect on creep rupture properties

• Cannot be painted

• Normal periods of outdoor storage present no loss in creep rupture strength. Addition of stabiliser products to improve UV resistance is required

• Can be painted

• UV resistant

• Corrosion could be a problem

• Can be painted

Thermal Expansion

• 0,2mm/m/°C • 0,07mm/m/°C • 0,012mm/m/°C

Abrasion (depends on type of material being pumped)

• 0,25mm after 600 000 cycles

• Wear rate 0,23

• 0,75mm after 600 000 cycles

• Wear rate 1,42

Flammability

• Normal fl ammability: ignites on contact with fl ame. Continues to burn when the ignition source is removed and melts with burning drips

• PVC pipe is self-extinguishing

• Non fl ammable

young’s Modulus

• 800 - 1100 Mpa (Short Term) • 3000 - 4000 MPa (Short Term) • 210 000 MPa

Regression Curves (stress / time relationship)

With plastic materials the relationship between

stress and strain is time dependant. This means that

if the stress is kept constant the strain will increase

with time. This is called the creep phenomenon. In

practical terms this creep means that failure will

occur after a certain loading period. As the time

to burst is inversely dependent on the stress it is

possible to determine a stress level at which the time

to failure will far exceed the pipeline’s design life.

All plastics used for the manufacture of pipeline systems are classifi ed and their allowable stress limits determined by long term performance under hydrostatic pressure in accordance with ISO 9080 (2003)

Classifi cation is achieved by testing pipe samples at different temperatures and internal pressures and recording the time to failure. The data is then extrapolated in accordance with ISO 9080 in order to predict the stress after 50 years. These results are plotted to give a regression curve. This classifi cation

PIPE MATERIAL CLASSIFICATION

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system is based on the predicted minimum required stress (MRS) that would cause failure after 50 years.

The 97.5% lower confi dence limit of the predicted stress is rounded down to give the MRS value for each manufacturer’s material.

The values given assume an operating temperature of 20°C. The MRS value increases at lower temperatures and vice versa. When designing pipelines for use at temperatures above 20°C the correct MRS value must be therefore be used for the given operating temperature.

As these regression curves are the basis for designing plastic piping, a detailed description of how they are constructed follows.

At a fi xed temperature the pipe is put under a fi xed hoop stress and the failure time t is measured. A range of hoop stresses are investigated (from 2 to 40MPa, depending on the polymer and the temperature), resulting in a range of failure times from 1 to 10 000 hours. The regression curve is calculated and presented as a log/log plot.

The long term hydrostatic strength (SLTHS) is the predicted mean strength at a given temperature, calculable over a time range from 1 hour to 50 years. It is extrapolated from the 20/40/60/80 degree C curves (failure times measured from 1h to 10 000h = 416 days). To ascertain the reliability of the extrapolation, the lower prediction limit sLPL is calculated:

• SLTHS (MPa): Long Term Hydrostatic Stress = predicted mean stress at a temperature T and time t.

• SLCL (MPa): Lower Confi dence Limit 97,5% = lower confi dence limit of the interpolated hydrostatic stress at a temperature T and a time t.

• SLPL (MPa): Lower Prediction Limit 97.5% = lower prediction (extrapolation) limit of the predicted (extrapolated) hydrostatic stress for a single value at a temperature T and a time t.

The failure can be either ductile (which corresponds to creep rupture) or brittle (which corresponds to environmental stress cracking). Ductile failure occurs at “high” hoop stress and gives a short failure time. Brittle failure occurs at “low” hoop stress and gives a long failure time. The two kinds of failure give rise to a linear curve made of two branches of different slope: almost horizontal for ductile failure (short failure time), and then steep for brittle failure (long failure time). The transition point between the 2 modes of failure, which is represented by a change of slope on the regression curve, is called the “knee” of the regressi on curve.

PVC as well as the latest grades of PE will not display a “knee” on the curves.

At between 60 and 80°C it may be possible to observe the knee before 10 000 h but at 20°C the knee should not be observed before 10 000 h - it can only be determined through extrapolation. As the behaviour of a resin can not be known before starting its regression curve, the exact failure times can not be predicted. In practice the creation of a regression could take 18 months or longer.

The permissible design stress is obtained by applying a safety factor (1,25 – 2,5) to the projected burst stress at 50 years.

PIPE MATERIAL CLASSIFICATION

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Example of regression curve displaying a “knee”.

Figure 5: Typical Regression Curve for Hydrostatic Stress

Time (Hours)

• re

fere

nce

Stre

ss (

MPa

)

Ductile failure is a creep induced failure, or plastic deformation – the pipe stretches and deforms under pressure. Ductile failure resistance can be enhanced by increasing the crystallinity and therefore the density of the polymer. The material is then stiffer. Brittle failure is the result of (age induced) environmental stress cracking (slow crack growth) through the disentanglement of the polymeric chains. It can be prevented by increasing the entanglement (higher molecular weight, chain branching).

In failure induced by creep, the failure time depends on the applied pressure. This means that a small change in pressure implies a large change in failure time. Conversely, environmental stress cracking / slow crack growth corresponds to an age induced degradation of the polymer. When the polymer becomes older, the polymeric chains disentangle themselves; micro cracks build and grow, so that the polymer loses its stress resistance.

PIPE MATERIAL CLASSIFICATION

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NOTES

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PART II SELECTION AND INSTALLATION

PART II SELECTION AND INSTALLATION .................................................................................. 19

HYDRAULIC REQUIREMENTS............................................................................................... 20

Basic Principles ......................................................................................................... 20

Operating Pressure, Hoop Stress and Wall Thickness ............................................................. 23

Surge and Fatigue ...................................................................................................... 24

Factory Tests ............................................................................................................ 25

EXTERNAL LOADS ........................................................................................................... 26

Design Basis ............................................................................................................. 26

Load Classifi cation ..................................................................................................... 26

Pipe Stiffness ........................................................................................................... 27

Determining Required Pipe Stiffness ................................................................................ 28

Vertical Defl ection ..................................................................................................... 30

DURABILITY REQUIREMENTS .............................................................................................. 31

Durability ................................................................................................................ 31

SYSTEM COMPONENTS ..................................................................................................... 31

Secondary loads ........................................................................................................ 31

Manholes ................................................................................................................ 31

Joints And Fittings ..................................................................................................... 31

Valves .................................................................................................................... 32

INSTALLATION ............................................................................................................... 32

Preconstruction Activities............................................................................................. 32

Excavation .............................................................................................................. 32

Embedment ............................................................................................................. 33

Pipe Laying and Jointing .............................................................................................. 33

Backfi lling ............................................................................................................... 34

Anchoring ................................................................................................................ 35

Site Tests ................................................................................................................ 35

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Basic Principles

The three principles used in the hydraulic design of pipelines are continuity, energy and momentum. The continuity principle states that the fl ow rate at one section of a pipeline will be the same as at any other section, provided there is no change in the discharge.

Q 1 = A 1 V 1 = Q 2 = A 2 V 2 (9)

The energy equation or Bernoulli expressed in SI units states that

V12/2g + p1/γ + Z1 = V2

2/2g + p2/γ + Z2 + hL(10)

V – velocity in m/s

g – acceleration due to gravity in m/s2

S – gradient in m/m

P – pressure in kPa

γ – unit weight of fl uid kN/m3

Z – height above datum in m

h – head loss between sections 1 and 2 in m

Q - Volumetric fl ow rate in m3/sec

The momentum principle states that the change in momentum between two sections of a pipeline equals the sum of the forces causing the change.

ΔFx = ρQΔVx (11)

F - force in direction x in kN/m2

ρ - unit mass of fl uid in kg/m3

Q - volumetric fl ow rate in m3/s

V - velocity in m/s

Subscript x refers to the velocity in the ‘x’ direction

The hydraulic capacity of any conduit will be determined by a combination of factors, namely the energy difference between the inlet and outlet, the geometric properties of pipe, pipeline alignment and the physical properties of pipe material. The energy losses in a pipeline are due to friction and transitions.

Friction is developed as a fl uid moves past the pipe wall. The rougher the surface the higher the energy required to overcome this friction.

In a pipe fl owing full, the energy to overcome friction is provided by the pressure gradient, where as in an open channel this energy is provided by the weight of the water running down the slope. In a closed conduit the friction resisting the fl ow is around the whole boundary. In an open channel there are two types of surfaces, a free air water interface where there is negligible friction and the interface between the fl uid and the pipe wall, where friction is developed.

In its simplest form the velocity through a conduit can be described by the Chezy equation.

V= C rS (12)

Where V - is the velocity

C - the Chezy coeffi cient

R - describes the conduit geometry

S - describes the gradient

There are several derivatives of this basic equation. Equations such as Manning and Hazen-Williams are based on empirical roughness values, whereas Colebrook-White is theoretically correct and based on absolute roughness values.

The empirical equations are easier to apply and are adequate for most applications.

Manning is used for both pipes fl owing full and partly full.

V = 1/n r S1/2 (13)

Where V - velocity

n - roughness coeffi cient

R - hydraulic radius

S - slope of energy line for pipes fl owing full (m/m)

slope of pipeline for pipes fl owing partly full (m/m)

1n

HYDRAULIC REQUIREMENTS

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Hazen-Williams is the preferred formula for pipes fl owing full and has a similar format.

V = 0.345CD0,63S0.54 (14)

Where V - velocity (m/s)

C - roughness coeffi cient

D - diameter in m

S - hydraulic gradient (m/m)

Values of the roughness coeffi cient for use in the Hazen Williams equation are given in table 4.

TABLE 4: PIPE rOUGHNESS COEFFICIENT

Pipe Material New 25 yrs old

50 yrs old

Badly corroded

PE, PP & PVC 150 140 140Do not corrode

Smooth concrete & FRC

150 130 120 100

Steel - Bitumen lined/galvanised

150 130 100 60

Cast iron 130 110 90 50

Vitrifi ed Clay 120 80Does not corrode

For diameters smaller than 1000mm reduce the value of C by

0,1 [1 - dia (mm)] c

Colebrook-White gives a more rigorous formula that accounts for the absolute roughness of the pipe material and the viscosity of the fl uid. The values are more accurate, but also more diffi cult to calculate and it is not so easy for the designer to develop a feel for how the formula responds to changes in the variables. It is expressed as:

V = -2 2gDS log(ks/3.7D + 2.51v/D 2gDS) (15)

Where ks - absolute roughness of pipe material (mm)

v - kinematic viscosity of fl uid (m2/s)

The other symbols are already defi ned. It should be noted that v is temperature dependant and this must be taken into account when accurate results are required.

A comparison of different absolute roughness values is given in Table 5.

TABLE 5: ABSOLUTE rOUGHNESS VALUES

Material k (mm)

Polyethylene & PVC 0,002

GRP 0,01

Steel, new 0,05

Galvanised Iron, new 0,15

Ductile Iron, new 0,5 – 1,0

Ductile Iron, corroded 1,0 – 1,5

For a quick determination of fl ow parameters the nomograph in Figure 6 can be used. However, when accurate values are required, they should be calculated.

HYDRAULIC REQUIREMENTS

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For practical reasons the velocities in pressure pipelines should fall in the range of 0.8 to 2.5 m/s. the lower limit to maintain self cleansing fl ow and the upper limit to minimize air release at high points.

The velocity range in gravity systems is the same with the proviso that downstream velocities should not be appreciably lower than upstream values, to prevent the deposition of the bed load being carried. (A drop in velocity to 0.7 of the upstream value is probably the maximum that should be allowed. Another factor to consider in pipes that fl ow partly full is super critical fl ow. When this occurs the velocity should not exceed 2.5 m/s. or the velocity head should be contained in the pipe.

Figure 6: Nomograph for solving Colebrook White. Applied to PVC or PE

HYDRAULIC REQUIREMENTS

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Figure 7: Flow in a pressure pipeline

The operating pressure at any section along a pressure pipeline will be determined by the vertical alignment and the energy losses that occur.

The total energy as described by Bernoulli’s equation, given earlier is applicable to all sections along a pipeline. The operating pressure will be the total head above the pipe invert less the velocity head. This internal pressure will generate stresses in the pipe wall.

The hydrostatic pressure capacity of plastic pipe is related to a number of variables:

• The ratio between the outside diameter and the wall thickness (standard dimension ratio)

• The hydrostatic design stress of the material

• The operating temperature

• The duration and variability of the stress applied by the internal hydrostatic pressure

Although plastic pipes can withstand short-term hydrostatic pressures at levels substantially higher than the pressure rating, the design is always based on the long-term strength at 20°C to ensure a design life of at least 50 years.

The relationship between the internal pressure, diameter, wall thickness and the hoop stress in the pipe wall, is given by the Barlow formula, which can be conservatively expressed as follows:

e = (16)

Where: P - internal pressure (MPa)

e - minimum wall thickness (mm)

Dm - mean pipe diameter (mm)

σs - hoop stress across the pipe wall (MPa)

This formula has been standardized for use in design, testing and research and is applicable at all levels of pressure and stress. For design purposes, P is taken as the maximum allowable working pressure and σs the maximum allowable hoop stress at 20°C.

Operating Pressure, Hoop Stress and Wall Thickness

P Dm2σs

HYDRAULIC REQUIREMENTS

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Figure 8: Internal Pressure in pipe

Dm2e

When this equation is used for the design of an installed pipe it is written:

σs ≤ PN (17)

where σs - permissible design stress (MPa)

PN - nominal pressure rating

Surge & Fatigue

It should be noted that the modern thermoplastics such as PE and PVC-O are very tolerant to the rapid loading which occurs with transient pressures. They develop great short term strength and stiffness as the structure of the materials’ molecular chain reacts to resist the deformation. Hence, at high pressurisation rates pipes are better able to resist the higher stress levels associated with surge. The strength of the material increases with high rates of loading.

Surge and fatigue are often combined as a single parameter. Although both phenomena arise from the events such as valves closing quickly and pump shut down, they should be considered separately, since they have a different effect on the pipe material.

Surge generates pressures that generally rise above the static rating of the pipeline and these pressures are applied over very short periods. The initial rate of pressure change is rapid but of short duration.

Fatigue is associated with cyclic pressure variations that are repeated over a long period. It is a condition often occurring below the rated pressure. This is not a problem with the slow daily pressure cycles which frequently occur in distribution systems, but in circumstances where short-term surges may be repeated at frequent intervals, there is concern that the pipes may weaken due to fatigue.

Fatigue response studies show that fatigue cracks initiate from a dislocation in the material matrix, usually towards the inside surface of the pipe, where stress levels are highest and propagate or grow with each stress cycle at a rate dependent on the magnitude of the stress. Ultimately the crack penetrates the pipe wall.

Typically surge occurs when valves are opened or closed or pumps are stopped. The maximum theoretical surge can be calculated from Joukowsky’s formula:

HYDRAULIC REQUIREMENTS

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The pressure change or surge in a pipe line (water hammer) can be determined by applying Joukowsky’s equation

H = C v/g (18)

Where H - change in head due to water hammer (m)

c - wave celerity through the pipe

material (m/s)

v - change in fl ow velocity of fl uid (m/s)

g - acceleration due to gravity (9,81m/s)

Values for wave celerity through various materials conveying water at 20ºC are given in table 5.

The elastic modulus of the pipe ER under surge pressure is temperature dependant. Applicable values for PE and PP are given in Table 6.

TABLE 5: WAVE CELErITy (m/s) FOr rANGE OF PIPES AT 20OC

SDr rating

Pressure rating (bar)

Wave Celerity C

(m/s)PE PP PVC-U PVC-M

SDR 33 6 204 215 340 266

SDR 26 9 229 240 420 297

SDR 17 12 258 290 485 342

SDR 11 16 290 370 560 383

SDR 9 20 368 405 625 637

25 416 601 486

TABLE 6: ELASTIC MODULUS IN N/mm2 OF PIPE MATErIALS SUBjECT TO SUrGE PrESSUrES

Temperature PE PP

20oC 1680 1470

40oC 1230 950

60oC 760 560

80oC 390

Values for wave celerity rate at 20oC in water are shown in Table 5.

Because PE has a low elastic modulus, the wave propagation rate and surge intensity are considerably lower than in elastic pipe material (steel, concrete).

In tests with PE pipes under dynamic pressure loading it has been shown that the pressure surges can with good approximation be calculated according to the pressure surge theory of Joukowsky.

Furthermore, it may be concluded from tests carried out by Lortsch that surges do not damage PE pipes provided that the mean stress is not higher than the stress at nominal pressure; i.e. for example with a SDR 17 (PN 6) pipe at an operation pressure of 6 bar at 20oC the mean pressure does not exceed 6 bar or a relative stress of 5 MPa. The surge amplitude in this case could be ± 6 bar.

Factory Tests

A comprehensive testing program is carried out at the plastic pipe factories to ensure that the performance requirements of the specifi cations are met. Of particular signifi cance to the designer are those that deal with the structural performance and water tightness. For details of these tests the reader is referred to the relevant SANS or ISO documents as listed in Table 2.

These tests, however, do not guarantee the performance of the installed pipeline. For this it is essential that the pipeline installation is checked and the necessary testing done on site.

HYDRAULIC REQUIREMENTS

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Design Basis

The strength of a buried pipe must be selected so that it will be strong enough to carry the most severe combination of loads that could be imposed on it. If the imposed loads exceed the pipe strength the pipe will fail.

The failure mode of a pipe can be due to its inability to handle circumferential or longitudinal loading. This section addresses the external loads which cause circumferential stress. Failure can occur due to high bending stresses in the walls of rigid pipes or the excessive vertical defl ection of fl exible pipes. Buckling is rarely a problem with plastic pipes.

For fl exible pipes the stiffness of the surrounding material is more important for limiting defl ection than the stiffness of the pipe itself, so controlled backfi ll is particularly important. The design process consists of determining the load and then ensuring that acceptable defl ection is not exceeded by using an embedment material that has the required properties and compaction.

Load Classifi cation

The loads imposed on a buried pipeline are due to primary forces such as soil loads, superimposed traffi c loads and internal pressures and secondary ones resulting from soil movements caused by the fl ow of water, temperature effects and settlement under buildings. The pipes provide the conduit and may or may not provide the structure designed to take the primary forces. The joints are designed to ensure that the conduit remains watertight and copes with secondary forces. The primary forces can be calculated, but the secondary forces cannot, hence they have to be estimated.

The primary loads on any buried pipe are infl uenced by the installation conditions and initially will be the same irrespective of the type of pipe material. However, the way in which the loads are carried will vary signifi cantly depending on the interaction of the components in the pipe/soil system. These components are the pipes, the virgin soil, the embedment material and the founding conditions as shown in Figure 9 below.

Figure 9: Comparison of rigid and fl exible pipe installation details

VIRGIN SOIL

BEDDINGBLANKET

RIGID PIPE

BACKFILL

FLEXIBLE PIPE

VIRGIN SOIL

EMBEDMENT

CRADLE

FOUNDATIONFOUNDATION

EXTERNAL LOADS

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The interaction of these components will determine how the pipe chosen will handle the load. Hence, any design guidelines must cover the interaction between them, describe what to do as they vary and where necessary, set limits to their structural properties.

For rigid pipes it is assumed that the reaction from the bedding cradle is vertical only. Hence it is only necessary to provide support around the bottom portion of the pipe. For fl exible pipes it is essential that the reaction from the surrounding material also gives side support. This means that the pipes should be encased in a suitable material at least up to the level of the pipe crown. In this case the supporting material is called embedment.

The earth load on a buried conduit is the mass of the earth prism directly above it that is either increased or decreased by the arching action resulting from the friction between adjacent columns of earth above and next to the pipe. The arching is dependent on installation type, founding conditions and properties of insitu and backfi ll materials:

• limiting installation types are narrow trench and complete embankment projection where the load is minimum and maximum respectively.

• limiting founding conditions are yielding and rigid, where the load is minimum and maximum respectively.

• the most signifi cant properties of the insitu and backfi ll materials are their mass, stiffness and friction angles. The friction angle is the most signifi cant for rigid pipes and the stiffness the most signifi cant for fl exible pipes.

In practice most pipelines are installed in conditions falling somewhere between these limiting cases. Irrespective of the pipe material the soil loads on the horizontal plain level with the top of the pipe, before any defl ection has taken place will be the same for any given installation. However, when the material on top of the pipeline is compacted, the critical plane which is the horizontal line over the top of the pipeline will deform either side of the pipeline line depending upon whether the frictional forces that develop will act upwards or downwards. With fl exible pipes that have the required side support, the pipes will settle more than the adjacent

material and the frictional forces will act upwards and reduce the load that the pipes have to carry. The worst combination of values for these limiting factors could result in loads that are in excess of twice the value of those for the most favourable conditions for the same fi ll height.

Traffi c loading is distributed from the contact areas on the surface through the fi ll. At fi ll heights greater than ±1.25m earth loads make a greater contribution than traffi c loads to the total load. At fi ll heights less than 600mm or half the conduit’s outside diameter traffi c and other transient loads are not uniformly distributed over the conduit and they cannot be evaluated in the same way as earth loads. Not withstanding the calculated radius it is recommended that the fi ll height over fl exible pipes under a roadway should be at least the larger of 900 mm or the pipe diameter.

Although gravity pipelines usually fl ow partly full, there are times when they may be pressurised due to operating conditions or problems such as blockages that occur. These pipes and their joints should therefore be designed and manufactured to cope with a nominal operating pressure of 1 bar, which is well within the capability of pipes supplied for these applications.

Pipe Stiffness

Various parameters are used to defi ne pipe stiffness. They all relate to the ability of a pipe to resist deformation. The incorrect understanding of these parameters can lead to serious overloading of pipes.

Pipe stiffness is obtained by subjecting a pipe to a parallel plate test.

PS = F/ΔL (19)

Where - PS is pipe stiffness

- F is the force necessary to defl ect the pipe by a given percentage taken from the relevant specifi cations

- ΔY is the vertical defl ection

This is usually expressed as kPa. kN( )m2/

EXTERNAL LOADS

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Pipe stiffness factor is calculated from the pipe material properties and the pipe geometry.

DIN PSF = EI/r3 (20)

Where - PSF is the pipe stiffness factor in kN/m/m

- E is the elastic modulus of pipe material

- I is the moment of inertia of the pipe wall

- r is the pipe radius

Pipe ring stiffness is also calculated from the pipe material properties and the pipe geometry. It is an eighth of the PSF.

ISO PrS = EI/D3 (21)

Where - PRS is the pipe ring stiffness in kN/m/m

- E is the elastic modulus of pipe material

- I is the moment of inertia of the pipe wall

- D is the pipe diameter

The relationship between these factors is:

0.149 PS = PSF = 8 PrS; PS = 6.71 PSF = 53.69 PrS (22)

TABLE 7: rELATIONSHIP BETWEEN PS, PSF AND PrS

PIPE STIFFNESS

kPA

PIPE STIFFNESS FACTOr

kN/m/m

PIPE rING STIFFNESS

kN/m/m

100 14.9 1.860

200 29.8 3.725

300 44.7 5.588

400 59.6 7.450

Determining Required Pipe Stiffness

The vertical soil is generally the dominant loading causing the defl ection of fl exible pipes or circumferential bending of rigid pipes. For fl exible pipes, irrespective of whether they are installed under embankment of trench conditions the vertical

pressure at the level of the top of the pipe can be evaluated using column theory:

WE = γHD (23)

Where: W - Downward, or geostatic load on pipe (kN/m)

H - Depth (m)

γ - Unit weight of the soil (kN/m )

D - External pipe diameter (m)

Most pipes are laid in trenches. The loading will be reduced by the friction and cohesion between the backfi ll material and the trench walls. Friction in the side of the trench supports some of the fi ll. The load in kN/m i.e. per unit length of trench of width B is thus:

WE = C1 γHB (24)

Where C1 is obtained from in Figure 10 as a function of H/B and k tan θ, k is the ratio of lateral to vertical soil stress and θ is the soil angle of friction.

Figure 10: Load coeffi cients for trench conditions

k TAN θ

C1

EXTERNAL LOADS

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When the side fi ll is correctly compacted, fl exible pipes deform more under load than the material adjacent to them. Load sheds to the side fi ll so the fi nal load on the pipe is less than what the column theory indicates. The actual soil load on a fl exible pipe will be:

WE = C1γHD (25)

The calculation of C1 involves determining the soil properties which can be complex. For practical reasons the conservative approach to calculating the load on a fl exible pipe can be done using equation (25) with C1 having a value of unity.

There are various ways of calculating the live loads on a buried pipe. Some of these are tedious to apply by hand and do not give answers that differ much from the simple approach of just distributing the load through the fi ll material at 45°, as shown in equation (26).

The load on a pipe in kN/m due to a live load of P at the surface is:

WL = P x D (26 )

(x + 2H)(y + 2H)

Where x and y are the footprint dimensions with formula of the load P at the surface. Other symbols defi ned elsewhere.

In service light fi eld loads are all a fl exible pipe should take. Heavier loads should be accommodated with sleeves or placing a concrete slab over the pipes. The live load WL could be corrected for load shedding, but as it is only a temporary load, it activates a higher pipe modulus, E, than the soil load does.

Figure 11: Wheel Load on Buried Conduit

However, during construction any buried pipeline could be subject to the same traffi c loads as roads, because there are deliveries to site. In South Africa the legal limits for road vehicles is a 40 kN wheel load. Table 8 has been compiled for two such vehicles parked next to each other with a space of 400 mm between them.

TABLE 8: : LOADS IN KN/M ON BUrIED CONDUITS FrOM A GrOUP OF 40KN WHEELS

PIPE OD FILL HEIGHT OVEr PIPES IN MMM 0.6 1.0 1.5 2.0 2.5 3.0 3.5 4.0 5.0 6.0 7.050 1.18 0.69 0.41 0.27 0.20 0.15 0.11 0.09 0.06 0.04 0.0390 2.13 1.25 0.74 0.49 0.35 0.26 0.20 0.16 0.11 0.08 0.06110 2.60 1.52 0.91 0.60 0.43 0.32 0.25 0.20 0.14 0.10 0.07160 3.79 2.21 1.32 0.88 0.63 0.47 0.36 0.29 0.20 0.14 0.11200 4.73 2.77 1.65 1.10 0.78 0.58 0.45 0.36 0.25 0.18 0.13250 5.92 3.46 2.07 1.37 0.98 0.73 0.57 0.45 0.31 0.22 0.17315 7.46 4.36 2.60 1.73 1.23 0.92 0.71 0.57 0.39 0.28 0.21355 8.40 4.91 2.93 1.95 1.39 1.04 0.80 0.64 0.44 0.32 0.24400 9.47 5.54 3.31 2.19 1.56 1.17 0.91 0.72 0.49 0.36 0.27450 10.65 6.23 3.72 2.47 1.76 1.31 1.02 0.81 0.55 0.40 0.30500 11.83 6.92 4.13 2.74 1.95 1.46 1.13 0.91 0.62 0.45 0.34560 13.25 7.75 4.63 3.07 2.19 1.64 1.27 1.01 0.69 0.50 0.38630 14.91 8.72 5.21 3.46 2.46 1.84 1.43 1.14 0.78 0.56 0.43710 16.80 9.83 5.87 3.90 2.77 2.07 1.61 1.29 0.87 0.63 0.48800 18.93 11.07 6.61 4.39 3.13 2.34 1.81 1.45 0.98 0.71 0.54900 21.30 12.46 7.44 4.94 3.52 2.63 2.04 1.63 1.11 0.80 0.611000 23.67 13.84 8.26 5.49 3.91 2.92 2.27 1.81 1.23 0.89 0.67

EXTERNAL LOADS

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Δd = W

PS + SS

Vertical Defl ection

The vertical defl ection of a fl exible pipe is limited by lateral soil resistance that develops as the pipe deforms horizontally into it. The load is carried through the arching action of the soil rather than circumferential bending of the pipe. Hence the wall stresses in a fl exible pipe are considerably less than those that develop in the walls of a rigid pipe. In simple terms the defl ection of a fl exible pipe is expressed in formula (27).

Where Δd - pipe defl ection

W – Load on pipe in kN/m

PS – Pipe stiffness in kN/m/m

SS - Soil stiffness in kN/m/m

This defl ection is usually determined using the Iowa formula or one of its derivatives, such as the reclamation formula (28)

(28)

Where Δd - vertical defl ection due to soil loads

D - pipe diameter

Tf - a dimensionless time lag factor, having a value between 1.5 and 3.0 that takes into account the increase in soil load with time and the consolidation of soil at the sides of pipes with time

KB - bedding constant, having a value between 0.11 and 0.083

γ - backfi ll density

H - fi ll height on pipe

EI/D3 - pipe ring stiffness

Fd - a dimension design factor varying from 0.5 to 1.0 depending on the effectiveness of side fi ll compaction. It converts average to maximum values of defl ection.

E1 - soil stiffness

Since E decreases with age the 50 year E value could be used for soil load defl ection calculation as a conservative assumption. For live loads a separate calculation using the short term E value could be used assuming the wall is not all stressed to the limit. The defl ections due to soil and live loads should then be added to give the total defl ection..

The deformation due to live loads is calculated from formula (29)

Where ΔdL - vertical defl ection due to live or traffi c loading

For low stiffness pipes such as PE and PVC that can tolerate signifi cant strain the defl ection is almost exclusively determined by the E1 of the soil and the use of short or long term E values for the pipe material will have little impact. It is essential therefore that the E1 value of the supporting material surrounding the pipe has a value of at least 5 MPa.

Note: There are also other useful design principles available.

Wall Stress

The maximum wall stress around the circumference of a pipe is due to a combination of ring bending under vertical load and arching. At the haunch it is :

f = W3

20 Et2/D2 + Es

(30) 2t 24 Et3/D3 + Es

It is recommended that installation conform strictly to the requirements of the relevant sections of the SABS 2001-4: 2008. This calls for a material with a low compaction factor to be compacted to 90% or more, of modified AASHTO density. This will result in an Es value of at least 5 MPa for selected material. Good bedding also reduces deflection, and circumferential wall stress in particular.

( )

Δd = D

TfkBγH

8EI/D3 + 0,061 FdE1

ΔdL =

D

kB WL/D

8EI/D3 + 0,061 FdE1

x

(27) (29)

EXTERNAL LOADS

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Durability

Probably the property of any pipelines that has the greatest impact on its long term performance are those that relate to the pipe material property and their ability to handle installation and operating conditions.

Plastics are in general inert to a very wide range of aggressive elements in the soil and in the effl uents that may be conveyed in a pipeline. Appendix B gives a comprehensive list of the chemical resistance offered by the thermoplastics used for pipe manufacture to a wide range of potentially aggressive substances. The effect of temperature which could be a signifi cant factor for industrial applications is also covered in these tabulations.

Material specifi c properties are covered in more detail in Part III of this document that covers the various pipe types.

Secondary Loads

Secondary loads are not easy as to determine as the primary loads, because they are variable, unpredictable and localised. They can however cause considerable damage to a pipeline due to differential movements between pipes and between pipes and other components. It is therefore essential that their potential impact be recognised and that where necessary precautions are taken. Examples of factors that could cause secondary loads are:

• Volume changes in clay soils due to variations in moisture content

• Pressures due to growth of tree roots

• Foundation and bedding behaving unexpectedly

• Settlement of embankment foundation

• Elongation of pipeline under deep fi lls

• Effects of thermal and moisture changes on pipe materials and joints

• Effects of moisture changes and movements on bedding

• Restraints caused by bends, manholes etc.

It is preferable to avoid or eliminate the causes of these loads rather than attempt to resist them. Where this is not possible, particular attention must be paid to pipe joints and the interfaces between the pipeline and other structures, such as manholes to ensure that there is suffi cient fl exibility. The reader is referred to the section in this handbook which deals with joints.

Manholes

Apart from the upper reaches of reticulation systems the access to pipelines is via manholes. Manholes are the interfaces between sections of pipeline where changes are made. They are placed whenever there are junctions, transitions and changes in alignment and where access is needed on long straight sections. As the loading on manholes is different from that on the adjacent sections of pipeline there can be relative movement between manholes and pipes.

Many of the failures in sewers occur at joints and in particular those at the interfaces where changes are made. If measures are not taken to minimize the disruption to fl ow through these manholes and the associated energy losses not considered the hydraulic performance of a sewer can be seriously compromised and if measures are not taken to accommodate any potential relative movement between pipes and manholes, pipes can crack or deform resulting in leakages.

Joints and Fittings

Most of the problems that occur in pipelines happen at joints between pipes, at bends, at junctions and at transitions. The making of joints can be complicated by site conditions, so it is essential that the necessary precautions and correct procedures are followed.

Joints and fi ttings can be both material and supplier specifi c and for these the reader is referred to the product brochures of the individual manufacturers. (A list of the SAPPMA members with contact details is given on the outside back cover.)

DURABILITY & SYSTEM COMPONENTS

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Valves

Air and scour valves are needed in pressure pipe lines to facilitate their fi lling, emptying and operation. Air accumulates at the high points in a pipeline where the operating pressure is low. This has the effect of reducing and at times stopping the fl ow.

For this reason air valves are placed at high points and other sections of pressure pipelines so that any air that accumulates is released.

Scour valves are placed at low sections of pressure pipelines so that they can be discharged for cleaning.

Preconstruction Activities

Following the correct design procedures is no guarantee that a pipeline will perform as required. It is essential that the design is based on the actual conditions on site and that the installation is in accordance with the specifi cations. Justly, the design must be preceded by a site investigation that establishes all the relevant topographical and geotechnical features and carries out the necessary material tests. Secondly, the design stage must be followed by supervising the construction to ensure that the correct installation procedures are followed and that the necessary onsite testing is done to check that the pipeline meets the required performance standards.

The satisfactory long term operation of any pipeline is thus dependant on the quality of design, manufacture and installation. It is therefore important that installation procedures be followed as detailed in:

• SANS 2001 Standard specifi cation for Civil Engineering Construction

• ISO TR 4191 PVC-U pipes for water supply - recommended practice for laying

• DD ENV (452 - 6 : 2002 Plastics Piping Systems for Water Supply (PVC-U) - Part 6, Guidance for installation.

What follows emphasizes the same important aspects about installation procedures.

Before pipe orders are fi nalized the contractor and consultant’s supervision should go through the

project documentation and check that the conditions on site correspond to those given and that if there are any discrepancies that these are resolved before installation starts.

Once these issues have been addressed the line, level and trench widths should be surveyed to ensure that there are no unforeseen obstructions to the route. If there are any, the necessary changes should be made.

Excavation

Trench excavation should be kept to a minimum width, allowing just suffi cient working area for jointing and embedment compaction around the pipe. For small diameter pipes a trench 300mm wider than the diameter of the pipe allows enough room for jointing. For pipes 300mm in diameter and larger the trench widths recommended in the relevant sections of SANS 2001 should be followed.

Figure 12:Trench Installation Details

It is important that the trench is not opened too far in advance of the pipe laying operation. Pipes must be backfi lled immediately after laying, with the joints left open for testing.

When the insitu soils have low E1 values it will be necessary to increase the trench width to accommodate additional embedment material to provide the pipes wih adequate lateral support. It is recommended that the depth of cover from the top of the pipe to the ground surface is not less than 0.9 metres or the pipe diameter, whichever is the greater.

INSTALLATION

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Embedment

The quality of the bedding material and its compaction, together with the nature of the undisturbed material of the trench wall are all relevant to the ultimate performance of all pipes once installed. The trench bed must be free from any stones or hard projections, which are likely to cause damage to the pipe. The bottom of the trench should be backfi lled to a depth of 100mm, with suitable bedding material such as free drainage coarse sand, gravel, or soil of a friable nature. The majority size of soil particles in the bedding material should not exceed 20mm. The presence of some particles of up to 40mm in size is permissible, providing that the total quantity of these particles represents a very small fraction of the whole and that these particles have no sharp edges. Reference should be made to SANS 2001-4: 2008 for the bedding specifi cation.

To determine the suitability of a soil for use as bedding material take a 2 kg sample of the material and pass it through a sieve with a nominal aperture size of 20mm. If the weight of material retained on the sieve exceeds 25 grams or if on passing the retained material through a sieve of nominal aperture size of 40mm particles are again retained and will not break up under light fi nger pressure, the material must be regarded as unsuitable.

If the material passes the sieve test as indicated above then proceed with testing as follows: Take a further sample of approx. 50 kg in mass, heap on a clean level surface. Using a spade, divide this heap through the middle in 2 separate heaps. Sub-divide one of the heaps again and again until a sample which will fi ll a 2,0 litre container is obtained.

Cut a length of 250mm from a pipe, 160mm in diameter, and stand this upright on a level surface. Ensure that the moisture content of this sample is the same as that of the main body from which it was taken and then loosely fi ll the pipe with this material. Empty the material from the pipe, into a suitable container. Using this same material charge the pipe in layers of 60mm in height, fi rmly tamping each layer with a metal hammer weighing between 1 and 1,25 kg and having a striking face of approximately 40mm in diameter.

Use up all material out of the container which originally was loosely fi lled into the pipe, tamping continually until no further compression of the material occurs. Measure the distance from the top of the pipe to the surface of the tamped material. If this measurement does not exceed 25mm then the material is suitable for use.

Figure 13:Testing suitability of bedding material

Pipe Laying and Jointing

The pipeline must be laid directly on the prepared bedding in the trench and any temporary supports, bricks or other foreign hard bodies must be removed. There are many joint types and the reader should refer to the particular supplier for their details.

By way of example the procedure for a typical PVC pipe joint is described herein. All spigots must be checked to ensure that they are free from burrs. Both the spigot and socket surfaces must be carefully cleaned with a dry cloth prior to the application of the gel lubricant.

It is important to ensure that the rubber ring is clean and free of stones and grit. It is however not necessary to remove the rubber ring as this has been fi tted in the factory and held fi rmly in position.

INSTALLATION

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Modern developments include steel reinforced rubber seals which cannot be dislodged on jointing and are user friendly especially unskilled installers.

Check the chamfer on the spigot end – a uniform chamfer to approximately 15° must occur around the external circumference of the pipe for approximately half the wall thickness.

The depth of entry is marked on the spigot end which must be so positioned as to be just visible outside the mouth of the socket. This allows for expansion and contraction in the pipeline.

Figure 14: Joining of PVC Pipes

Backfi lling

It is essential that plastic pressure pipes are backfi lled immediately after each pipe is installed, in order to contain the expansion and contraction that may occur in an open trench. Immediate backfi lling restricts expansion and contraction to each individual pipe length where it is catered for by the integral socket.

Before doing the side-fi lling and initial backfi lling check that the depth of entry mark is just visible on all joints. Selected material (as for bedding) should be placed gently and evenly in uncompacted layers of 75mm in thickness between the sides of the trench and the pipe, as shown in Figure 15 .Tamp each layer fi rmly with a hand tamper until the level of the crown of the pipe is reached, taking care to ensure that no voids are left under the pipe. All joints must be left exposed at this stage.

Movement of the pipe should be prevented by the fi lling and compaction of material simultaneously on either side of the pipe until level with the top of the pipe.

Selected material should be placed in even and uncompacted layers of 150mm in thickness over the entire width of the trench to a height of 300mm

above the crown of the pipe. All layers must be fi rmly tamped by hand. All joints are still exposed at this stage.

Figure 15:Bedding and Backfi ll Details

The main backfi ll for the remainder of the trench, excluding the areas where joints must still remain exposed, should be placed and compacted in 300mm thick layers. Excavated trench material can be used. Each layer must be fi rmly tamped, the fi rst layer by hand and subsequent layers by mechanical means if so required. The main backfi ll should be compacted to the same density as the surrounding insitu material. The fi nal level to which the trench is backfi lled should be slightly higher than the natural ground level to accommodate the consolidation of the backfi ll material in the trench.

INSTALLATION

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Cutting to Length

When cutting pressure pipe, clearly mark the cutting position on the pipe, ensuring that the cut is square to the axis of the pipe. Use a fi ne-toothed saw or power saw to cut the pipe. Remove all burrs from the cut end and chamfer the pipe with a fi ne medium fi le, at 15o to half of the pipe wall thickness. Redraw the depth of entry mark.

Site Tests

Any pipeline that is to convey water under pressure must be pressure tested, as soon as possible after it is installed to check the integrity of installation. Only when any required remedial work has been done and if necessary the pipeline has passed a retest should the pipeline be backfi lled. Both pressure and gravity pipelines should be checked with a CCTV camera after installation to check if there are any internal faults such as excessive defl ections, open joints and local damage. Any defects, no matter how small, that could result in the future malfunctioning of the pipeline must be rectifi ed before the pipelineis commissioned.

Anchoring

When an internal hydrostatic pressure is applied to the pipe, unbalanced forces develop at all changes of size and direction in a pipeline. Thrust blocks prevent the movement of fi ttings and must be placed at all changes of direction, valves, stop ends and reducers.

Concrete thrust blocks are the most commonly used at all anchor points. The dimensions of the thrust blocks must be calculated to suit the pipe diameter, pressure and the load bearing capacity of the soil. Typical thrust block sizes are given in Table 9. The actual size required for a particular project should be calculated and specifi ed by the design engineer.

In recent years mechanical restraint joints have become an alternative option to concrete anchor blocks insome cases.

TABLE 9: TYPICAL THRUST BLOCK SIZES

Pipe Sizes (mm) 90º Bends AxB 45º Bends AxB Tees AxB End Caps, Valves, reducers AxB

110 0.30x0.30 m 0.30x0.25 m 0.30x0.30 m 0.30x0.60 m

200 0.45x0.70 m 0.30x0.70 m 0.45x0.60 m 0.45x0.80 m

315 0.60x1.30 m 0.60x0.90 m 0.60x0.90 m 0.60x1.00 m

400 1.00x1.60 m 1.00x1.20 m 0.80x1.50 m 0.80x1.50 m

INSTALLATION

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Pipe Size Horizontal (mm) Vertical (mm)

40 400 1200

50 500 1200

75 800 1600

110 900 1800

160 1000 2000

Nominal Size (mm) Span between support (mm)

55 250

90 325

105/110 350

155/160 450

200/210 500

250 550

215 575

355 600

400 650

36 SAPPMA TECHNICAL MANUAL | jANUAry 2011 | 3rd Edition

INSTALLATION

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PART III PLASTIC PIPE PROPERTIES ....................................................................................... 37

POLYETHYLENE (PE) ....................................................................................................... 38 Typical Physical Properties ........................................................................................... 38 Benefi ts of PE ............................................................................................................38 Polymers ................................................................................................................. 38

Applications ............................................................................................................. 39 Benefi ts of PE 100 ...................................................................................................... 40 Design .................................................................................................................... 40 Other Relevant Values ................................................................................................. 44 PE in Gas Distribution ................................................................................................. 44 Cost Benefi ts of PE ..................................................................................................... 45 Pipe Dimensions ........................................................................................................ 45 POLYVINYL CHLORIDE (PVC) .............................................................................................. 50 Composition of PVC Pipe material ................................................................................... 50 Physical Properties ......................................................................................................50

Benefi ts of PVC ......................................................................................................... 51 Applications of PVC Pipe Systems ....................................................................................52 Design .....................................................................................................................52 Pipe Dimensions .........................................................................................................55 Strength and Toughness ............................................................................................... 62 Effect of Temperature Change ....................................................................................... 63

POLYPROPYLENE (PP) ...................................................................................................... 65 Benefi ts and Specifi cations ............................................................................................65

POLYETHYLENE JOINTING SYSTEMS ......................................................................................66 Polyethylene Welding Processes ......................................................................................66

Heated - Tool Socket Welding .........................................................................................68 Welder Training and Qualifi cations ...................................................................................71 Welding Equipment .....................................................................................................72 Destructive Test .........................................................................................................72 Air Test ....................................................................................................................73 Hydraulic Pressure Test ................................................................................................73 Minimal Dimensional Requirements for Fittings ....................................................................74 Fabricated Fittings (HDPE & PP) ..................................................................................... 76 Segmented Bends ...................................................................................................... 79 Seamless Long Radius Bends Plain Ended .......................................................................... 80 Electrofusion Socket Dimensions .................................................................................... 81 Spigot Dimensions ...................................................................................................... 82

HOT & COLD WATER PRESSURE PIPES ................................................................................... 83 Introduction .............................................................................................................83 Classifi cation ............................................................................................................ 84

APPENDICES ..................................................................................................................87 Appendix A: Identifi cation of Plastics ................................................................................87 Appendix B: Chemical Resistance of Thermoplastics used for pipes ............................................88

ABOUT SAPPMA ........................................................................................................... 100

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PART III PLASTIC PIPE PROPERTIES

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Typical physical properties

Physical Properties

Test method

Values Unit

Density ISO 1183 0,958 g/cm3

Melt Flow Index (190oC/21.6Kg)

ISO 1133 6,5g/10 min.

Melt Flow Index (190oC/5Kg)

ISO 1133 0,23g/10 min.

Vicat Softening Point (5Kg)

ISO 306 67 oC

Crystalline Melting Range

ISO 3146-85130-133

oC

Viscosity Number ISO 1628-3 390 cm3/g

Mechanical Properties

Test Method

Values Unit

Shore D, Hardness ISO 868 61 -

Tensile Yield ISO 527 25-30 MPa

Ultimate Tensile ISO 527 35 MPa

Ultimate Elongation ISO 527 >600 %

Elastic Modulus ISO 527 >800 MPa

Flexural Stress (3.5% Defl ection)

ISO 178 19 MPa

Notched Impact (Charpy) acN 23oC

ISO 179 20KJ/m2

Notched Impact (Charpy) acN - 30oC

ISO 179 6KJ/m2

Thermal Stability 200oC

ISO 10837

>60 min.

Carbon Black Content

ASTM D 1603

2.0-2.5 %

Benefi ts of PE

• High impact strength

• Excellent corrosion resistance

• Very good chemical resistance

• Excellent abrasion resistance

• Chemically inert and unaffected by acidic soil conditions

• Biologically inert against micro organisms

• Can be fusion welded, ensuring absolutely leak free joints

• Very smooth bore and low friction loss (k=0,002mm and C=150) and maintaining this smoothness throughout its useful life

• Low mass (about 1/8 of steel) and ease of handling

• High fl exibility, enabling long lengths to be coiled

• Inherent resistance to effects of ground movement

• Non toxic and safe for drinking water

• Low installation cost and maintenance free

• Large range of sizes, from 16 – 2 000 mm

• Very suitable for rehabilitation of old pipelines through trenchless technologies

Polymers

In the fi rst generation of PE the curve at 60°C and 80°C showed a knee before 10 000h, making it possible to calculate the co-ordinates of the knee at 20°C by extrapolation. They were generally stiff polymers of high density, but unsatisfactory slow crack growth resistance at 80°C. With the second (PE80-1980) and third (PE100-1990) generations of PE there is no knee anymore at 60°C and even at 80°C, with hardly ever any brittle failure before 10 000h.

Second generation polymer development resulted in improvements to the slow crack growth mechanism by increasing the chain branch content of the polymer. This resulted in a MDPE PE 80 pipe resin which had the added benefi cial characteristic of fl exibility that allowed long lengths of pipe to be coiled. This made it suitable for low cost installation.

POLYETHYLENE (PE)

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The third generation resins were formed by new production technologies, in particular the manufacture of bi-modal polyethylene resins. The science of molecular design recognised that the placement of the co-monomer branches in a specifi c part of the molecular weight distribution could signifi cantly retard the slow crack growth properties of a PE resin, without affecting the creep resistance performance. The increased strength and toughness of these resins allowed a new classifi cation of PE resins to be developed – PE 100.

Polymer Classifi cation

Designation Classifi cation MrS (MPa)

Design Stress (MPa) Water

PE100 10,0 8,0

PE80 8,0 6,3

PE63 6,3 5,0

Applications

Some typical applications of PE pipes are listed below:

Water supply

Polyethylene pipes offer distinct advantages over other materials (e.g. steel, fi bre cement, concrete, etc.) especially when used for water supply and in areas with a high water table, in which their installation is simplifi ed by jointing outside the trench.

Some examples:

• Potable water reticulation

• Sewage works

• Water Works & Water Treatment Plants

Furthermore, because of their fl exibility and low weight, they are ideal for use in underwater environments in various applications, such as outfall sewers.

Mining (Surface and Underground)

Polyethylene pipes have yielded excellent results when used in mining applications. Owing to their high abrasion and corrosion resistance, ease of handling and installation and their high mechanical strength, they are ideal for -

• Tailings (slurries and effl uents)

• Irrigating leaching piles

• Acid and alkaline solutions

• Concentrate pipelines (Reduction works and Drainage)

• Fire fi ghting installations

• Drinking water lines

• Chilled water lines

• Compressed air lines

• Ventilation ducting

• Vacuum lines (Drum fi lter)

Agriculture/Irrigation

PE pipes have various uses in agriculture and non-permanent couplings allow rapid coupling and uncoupling. Because it is fl exible it can be coiled, which facilitates transport 50m, 100m or longer coils.

Some applications are:

• Spray irrigation (Acids, Ammonia, Brine, Carbon Dioxide, Sugar solutions, Syrups, Fertilizers, etc.)

• Water pipes

Fishing

In the fi shing industry, the use of PE pipes is increasing. Because of their lightweight and ease of handling, resistance to salt water and attack by marine organisms, they are ideal for these applications, amongst others:

• Salmon breeding cages

• Maritime discharge and suction (Abalone farms)

• Salt water

POLYETHYLENE (PE)

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Chemical/Steel/Refi neries

In the chemical industry, PE pipes have produced excellent results. Owing to their high resistance to corrosion, chemicals and abrasion, they are ideal for:

• Conveying acid and alkaline solutions

• Conveying chemical products (Bleach, Peroxides, Dye Liquors, Sulphide Water, Hot effl uent)

• Conveying water under pressure

• Fire-fi ghting systems

Gas Distribution

PE is the preferred material for natural gas distribution pipelines in most countries in the world. In SA natural gas is not yet available for general consumer applications, although there are promising indications that it might change. At that stage, it will become necessary to include the relevant design information in this Manual.

General

PE pipe systems have been used successfully in many applications, both general as well as highly specialised, in industrial and civil sectors.

The most common applications are the following:

• Compressed air and ventilation air

• Protection of electrical and telephone cables

• High temperature liquids and gases

• Gas, petroleum and its derivatives

• Corrosive waste water, hot effl uents

• Potable Water

• Pneumatic transport

• Drainage and Sub-Soil Drainage

• Dewatering

Benefi ts of PE 100 vs PE 80

In the early 1990s, a new type of PE material was developed in Europe with higher hoop strength giving rise to the PE100 classifi cation. These materials are sometimes termed bimodal or 3rd generation because of the two stage polymerisation process used to produce them. PE100 materials produce stronger pipes which are used for higher pressure operation in gas and water distribution systems.

Example: 200 mm OD Pipe with water as fl uid at 10 bar operating pressure

Heading Wall thick-ness

Mass (kg/m)

ID (mm)

Cross Sectional area (cm

2)

PE 80 14.7 8.63 169.6 226

PE 100 11.9 7.10 175.5 242

Comparative saving in mass 18% and increase in cross sectional area 7%

Design

PE100 polymer pipe therefore provides the opportunity to choose either:

• Higher operating working pressure

• Thinner walls and therefore less material

• Higher safety margin

• Bigger cross sectional area and improved fl ow

Design Stress and Safety Factor (service factor)

Safety factors take into account handling conditions, service conditions and other circumstances not directly considered in the design.

In terms of SABS ISO 4427 the minimum safety factor for water is 1.25. This factor, when applied to the Minimum Required Strength (MRS), for the particular material classifi cation (e.g. PE80, PE100), gives the maximum allowable hydrostatic design stress for the designated material.

POLYETHYLENE (PE)

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Designation of material

MrS at 50 years and 20°C MPa

Maximum allowable hydrostatic design stress for water,

σ - MPa

PE 100 10 8

PE 80 8 6.3

PE 63 6.3 5

e =

Where: e - minimum wall thickness (mm)

p - internal pressure (MPa)

D - outside diameter (mm)

σ - design stress (MPa)

For example the minimum wall thickness for a 250 mm Class 10 PE pipe made from PE 80 material is:

e - 1.0 x 250 / {(2 x 6.3) + 1.0}

- 18.38 mm

Round up to 18.4 mm for manufacture and/or the appropriate SDR for the Class and Material designation.

Minimum required Strength (MrS) and Design Stress

The MRS (minimum required strength) classification of pipe is based on a 50 year life. This does not mean that the pipe will fail at 50 years, because the design stress is calculated using the 97.5% lower confidence limit of the predicted stress, coupled with a minimum safety factor of 1.25 (for water). Consequently when in service, the pipe is operating well below the stress that would cause a failure at 50 years and the actual failure time due to creep is likely to be only after hundreds of years.

MRS values usually assume an operating temperature of 20°C. The MRS value increases at lower temperatures and decreases at higher temperatures; therefore when designing pipelines for use at temperatures above 20°C the correct MRS value must be used for the given operating temperature.

The design stress used to calculate standard pipe dimensions for a given pressure duty is obtained by dividing the MRS by a safety factor C (or design coeffi cient). The safety factor adopted by ISO from fi eld experience is a minimum of 1,25 for water and 2,0 for gas.

The main criteria to select a good pipe material are:

• Strength

• Stiffness (or fl exibility)

• Ductility (in toughness)

• Chemical resistance

All these properties are time-dependent and therefore a compromise must be made on the basis of both short-term and long-term properties for a particular application as indicated below:

The choice of polymer should be based upon the optimal balance of those properties.

External or internal stresses occurring at elevated temperatures can cause environmental stress cracking in polyethylene. This is essentially slow rate crack growth and can be accelerated by a chemical environment other than air or water.

Environments that can accelerate crack growth are agents such as:

• Detergents

• Alcohols

• Silicone products

PDm 2σ

PD 2σ+P

e = i) ii)

POLYETHYLENE (PE)

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relevance of Material Properties

Property Effect

Ductility Impact resistance; Resistance to rapid crack propagation (RCP)

Strength Resistance to internal pressure

Stiffness Resistance to loading

Flexibility Deformation under stress

Chemical resistance (ESCR) Resistance to slow crack growth

Poly

mer

G

radi

ng

MrS

MPa

50

yr

20°

C

Des

ign

Coef

f.

For

wat

er 2

0° C

Max

des

ign

stre

ss M

Pa

Test

str

ess

MPa

16

5 hr

s 80

° C

Test

str

ess

MPa

20

° C

100

hrs

Test

str

ess

MPa

80

° C

1000

hrs

Not

ched

hoo

p st

ress

ba

r 8

0° C

500

hr

Wal

l Th

ickn

ess

mm

*

PN N

omin

al

Pres

sure

Bar

SDr

Pipe

ser

ies

PE 100

10 1,25 8.0 5.4 12,4 5,0 9.2 10,0 16 11 5

8,1 12,5 13,6 6,3

6,6 10 17 8

PE 80 8 1,25 6.3 4.5 10.0 4,0 8.0 10,0 12,5 11 5

8,1 10 13,6 6,3

6,6 8 17 8

PE 63 6,3 1,25 5.0 3.5 8,0 3,2 6.4 10,0 10 11 5

8,1 8 13,6 6,3

6,6 6,3 17 8

* Example of 110 mm OD Pipe

POLYETHYLENE (PE)

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The Stress regression Line

The traditional method of portraying the long term tensile strength is by means of a graph of log stress vs log time to failure. This is known as the stress regression line. It is a plot of the circumferential hoop stress in the wall of the pipe (from internal pressure) against time to failure.

Numerous test results are needed to determine both the classifi cation of the resin and to ensure that no ductile- brittle “knee” is observed before 50 years at 20°C. Testing is performed over a range of pipe pressures and temperatures (typically 20°C, 60°C 80°C) with a minimum of 30 hoop stress results being obtained at each temperature. There must be at least four pipes that do not fail before 7000 hours and one that does not fail untill after 9000 hours.

The data produced can then be used to defi ne the linear regression with the line extrapolated to 50 years at 20°C thus allowing the material classifi cation to be determined (refer ISO 9080 & SANS/ISO 4427).

The hoop stress is derived from Barlow’s formula and is as follows:

e =

2σ e + eP = PD

σ = P (D-e) 2e

where: p - internal pressure (MPa)

e - minimum wall thickness (mm)

D - outside diameter (mm)

σ - circumferential hoop stress in wall of pipe (MPa)

The Stress Regression Line for PE is given below.

Refer to general explanation of regression lines on page 15

REGRESSION CURVE OF A MODERN PE 100 MATERIAL

PD 2σ+P

POLYETHYLENE (PE)

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Other relevant values

Bending limit

The minimum bending radius permitted for a pipe depends on its pressure class (PN, SDR), the elastic modulus of the material and its permissible stress, which in turn vary as a function of the applied load and the temperature.

The following table lists the values suggested for the minimum bending radii of Polyolefi n pipes.

SDr Min. bending radius - PE

Min. bending radius - PP

33 40D 45D26 30D 25D17 30D 25D11 30D 20D

D = OD of pipe

Abrasion resistance

Dry sliding abrasion of a number of PE 80, PE 100 and some other grades of thermoplastic materials (Taber Abrasion Method in accordance with DIN 53754 E)

PE in Gas Distribution

The high cost of the replacement of corroded iron and steel mains led to the focus being shifted to Plastics in the 50’s. Many types of plastics were considered and tested as a material for gas distribution and by the end of the 60’s it was concluded that polyethylene offered the best answers to the important aspects of:

• Ductility

• Injection moulded fi ttings

• Jointing by fusion

Gas pipe operating pressures are classifi ed as follows:

• Low pressure up to 100mbar

• Medium pressure up to 4 bar

• Intermediate pressure 5 to 19 bar

• High pressure 50 to 70 bar

High pressure lines make use of polyethylene coated steel pipes with cathodic protection. For distribution systems operating below 4 bar, polyethylene is the most suitable material - technically as well as economically; even for 200mm pipes polyethylene still represents a 15% cost saving on the installed system (European basis). Over 90% of the pipe installed for natural gas distribution in the U.S. and Canada is plastic and of that, 99% is polyethylene. PE is the material of choice worldwide.

POLYETHYLENE (PE)

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Cost Benefi ts of PE

Installed Cost in rural Area (ratio steel/PE)

Diameter (mm)

80 100 150 200

Material 1,1 1,0 0,9 0,7

Laying 1,3 1,4 1,7 1,8

Trenching/Finishing

1,2 1,2 1,2 1,2

Overall 1,21 1,21 1,22 1,14

Installed Cost in City (ratio steel/PE)

Diameter (mm)

80 100 150 200

Material 1,1 1,0 0,9 0,7

Laying 1,3 1,4 1,7 1,8

Trenching/Finishing

1,3 1,3 1,3 1,3

Overall 1,29 1,28 1,3 1,22

Pipe Dimension

In this table it can be seen that SANS ISO 4427 have grouped together the different pressure classes, produced from different material designations, under a common heading known as the Standard Diameter (Dimension) Ratio or SDR.

The minimum wall thicknesses specifi ed are not exactly that which would be derived from a calculation using Barlow’s formula or the SDR but are the rounded up values of the highest minimum wall thickness calculated for any size and class in the SDR group.

POLYETHYLENE (PE)

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Pipe seriesSDR 6 SDR 7,4 SDR 9 SDR 11 SDR13,6 SDR 17

S 2,5 S 3,2 S 4 S 5 S 6,3 S 8

Nominal pressure (PN) a

bar

PE 80 PN 25 PN 20 PN 16 PN 12,5 PN 10 PN 8

PE 100 _ PN 25 PN 20 PN 16 PN 12,5 PN 10

Wall Thicknesses b

mmNominal

size

emin emax emin emax emin emax emin emax emin emax emin emax

16 3.0 3,4 2,3 c 2,7 2,0 c 2,3 _ _ _ _ _ _

20 3,4 3,9 3,0 3,4 2,3 c 2,7 2,0 c 2,3 _ _ _ _

25 4,2 4,8 3,5 4,0 3,0 3,4 2,3 c 2,7 2,0 c 2,3 _ _

32 5,4 6,1 4,4 5,0 3,6 4,1 3,0 3,4 2,4 2,8 2,0 2,3

40 6,7 7,5 5,5 6,2 4,5 5,1 3,7 4,2 3,0 3,5 2,4 2,8

50 8,3 9,3 6,9 7,7 5,6 6,3 4,6 5,2 3,7 4,2 3,0 3,4

63 10,5 11,7 8,6 9,6 7,1 8,0 5,8 6,5 4,7 5,3 3,8 4,3

75 12,5 13,9 10,3 11,5 8,4 9,4 6,8 7,6 5,6 6,3 4,5 5,1

90 15,0 16,7 12,3 13,7 10,1 11,3 8,2 9,2 6,7 7,5 5,4 6,1

110 18,3 20,3 15,1 16,8 12,3 13,7 10,0 11,1 8,1 9,1 6,6 7,4

125 20,8 23,0 17,1 19,0 14,0 15,1 11,4 12,7 9,2 10,3 7,4 8,3

140 23,3 25,8 19,2 21,3 15,7 17,4 12,7 14,1 10,3 11,5 8,3 9,3

160 26,6 29,4 21,9 24,2 17,9 19,8 14,6 16,2 11,8 13,1 9,5 10,6

180 29,9 33,0 24,6 27,2 20,1 22,3 16,4 18,2 13,3 14,8 10,7 11,9

200 33,2 36,7 27,4 30,3 22,4 24,8 18,2 20,2 14,7 16,3 11,9 13,2

225 37,4 41,3 30,8 34,0 25,2 27,9 20,5 22,7 16,6 18,4 13,4 14,9

250 41,5 45,8 34,2 37,8 27,9 30,8 22,7 25,1 18,4 20,4 14,8 16,4

280 46,5 51,3 38,3 42,3 31,3 34,6 25,4 28,1 20,6 22,8 16,6 18,4

315 52,3 57,7 43,1 47,6 35,2 38,9 28,6 31,6 23,2 25,7 18,7 20,7

355 59,0 65,0 48,5 53,5 39,7 43,8 32,2 35,6 26,1 28,9 21,1 23,4

400 _ _ 54,7 60,3 44,7 49,3 36,3 40,1 29,4 32,5 23,7 26,2

450 _ _ 61,5 67,8 50,3 55,5 40,9 45,1 33,1 36,6 26,7 29,5

500 _ _ _ _ 55,8 61,5 45,4 50,1 36,8 40,6 29,7 32,8

560 _ _ _ _ 62,5 68,9 50,8 56,0 41,2 45,5 33,2 36,7

630 _ _ _ _ 70,3 77,5 57,2 63,1 46,3 51,1 37,4 41,3

710 _ _ _ _ 79,3 87,4 64,5 71,1 52,2 57,6 42,1 46,6

800 _ _ _ _ 89,3 98,4 72,6 80,0 58,8 64,8 47,4 52,3

900 _ _ _ _ _ _ 81,7 90,0 66,2 73,0 53,3 58,8

1000 _ _ _ _ _ _ 90,2 99,4 72,5 79,9 59,3 65,4

POLYETHYLENE (PE)

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Pipe seriesSDR 21 SDR 26 SDR 33 SDR 41

S 10 S 12,5 S 16 S 20

Wall Thickness b

mmNominal

size

emin emax emin emax emin emax emin emax

16 _ _ _ _ _ _ _ _

20 _ _ _ _ _ _ _ _

25 _ _ _ _ _ _ _ _

32 _ _ _ _ _ _ _ _

40 2,0 c 2,3 _ _ _ _ _ _

50 2,4 2,8 2,0 2,3 _ _ _ _

63 3,0 3,4 2,5 2,9 _ _ _ _

75 3,6 4,1 2,9 3,3 _ _ _ _

90 4,3 4,9 3,5 4,0 _ _ _ _

110 5,3 6,0 4,2 4,8 _ _ _ _

125 6,0 6,7 4,8 5,4 _ _ _ _

140 6,7 7,5 5,4 6,1 _ _ _ _

160 7,7 8,6 6,2 7,0 _ _ _ _

180 8,6 9,6 6,9 7,7 _ _ _ _

200 9,6 10,7 7,7 8,6 _ _ _ _

225 10,8 12,0 8,6 9,6 _ _ _ _

250 11,9 13,2 9,6 10,7 _ _ _ _

280 13,4 14,9 10,7 11,9 _ _ _ _

315 15,0 16,6 12,1 13,5 9,7 10,8 7,7 8,6

355 16,9 18,7 13,6 15,1 10,9 12,1 8,7 9,7

Nominal pressure (PN) a

bar

PE 80 PN 6 d PN 5 PN 4 PN 3,2

PE 100 PN 8 PN 6 c PN 5 PN 4

POLYETHYLENE (PE)

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Wall Thicknesses b

MMNominal

size

emin emax emin emax emin emax emin emax

400 19,1 21,2 15,3 17,0 12,3 13,7 9,8 10,9

450 21,5 23,8 17,2 19,1 13,8 15,3 11,0 12,2

500 23,9 26,4 19,1 21,2 15,3 17,0 12,3 13,7

560 26,7 29,5 21,4 23,7 17,2 19,1 13,7 15,2

630 30,0 33,1 24,1 26,7 19,3 21,4 15,4 17,1

710 33,9 37,4 27,2 30,1 21,8 24,1 17,4 19,3

800 38,1 42,1 30,6 33,8 24,5 27,1 19,6 21,7

900 42,9 47,3 34,4 38,3 27,6 30,5 22,0 24,3

1000 42,9 47,3 34,4 38,3 27,6 30,5 22,0 24,3

NOTE 1 bar = 0,1 MPa = 105 Pa; 1 MPa = 1 N/mm2

a PN values are based on C = 1,25b Tolerances in accordance with ISO 11922-1:1997, grade V, calculated form (0,1emin+0,1)mm rounded up

to the next 0,1mm. For certain applications for e > 30 mm, ISO 11922-1:1997, grade T, tolerances may be used calculated from 0,15emin rounded up to the next 0,1 mm.

c The calculated value of emin according to ISO 4065 is rounded up to the nearest value of either 2,0, 2,3 or 3,0. This is to satisfy certain national requirements. For practical reasons, a wall thickness of 3,0 mm is recommended for electrofudion jointing and lining applications.

d Actual calculated values are 6,4 bar for PE 100 and 6,3 bar for PE 80.

Pipe series

SDR 21 SDR 26 SDR 33 SDR 41

S 10 S 12,5 S 16 S 20

Nominal pressure (PN) a

bar

PE 80 PN 6 d PN 5 PN 4 PN 3,2

PE 100 PN 8 PN 6 c PN 5 PN 4

POLYETHYLENE (PE)

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PE PE 100 (Orange) pipe, SABS ISO 4437 (Supply of Gaseous Fuels)

NOMINAL DIAMETEr

D mm

STANDArD DIMENSIONS rATION SDr(1)

SDr 17.6 SDr 11NOMINAL PrESSUrE - PN(2)

PN6 PN10 OVALITy(4)

e(3) ID Kg/M e ID Kg/M Straight Coiled16 2.3 11.2 0.10 3 9.8 0.12 1.2 1.220 2.3 15.2 0.13 3 13.8 0.16 1.2 1.2

25 2.3 20.2 0.17 3 18.8 0.21 1.2 1.532 2.3 27.2 0.22 3 25.8 0.28 1.3 240 2.3 35.2 0.2B 3.2 32.3 0.43 1.4 2.450 2.9 44.0 0.44 4.5 40.4 0.67 1.4 363 3.6 55.5 0.69 3.8 50.9 1.06 1.5 3.875 4.3 66.1 0.9B 6.8 60.9 1.47 1.6 4.490 5.2 79.2 1.42 8.2 72.9 2.14 1.8 5110 6.3 97.0 2.09 10 89.3 3.17 2.2 6125 7.1 110.3 2.6B 11.4 101.3 4.11 2.5 -140 B 123.5 3.3B 12.7 113.7 5.12 2.8 -160 9.1 141.2 4.3B 14.5 129.7 6.73 3.2 -180 10.3 158.8 5.57 16.4 146.0 8.50 3.6 -200 11.4 176.5 6.84 18.2 162.2 10.48 4 -225 12.8 190.7 B.62 20.5 182.5 13.27 4.5 -250 14.2 220.0 10.64 22.7 203.0 16.32 5 -280 15.9 247.2 13.39 25.4 227.4 20.46 9.8 -315 17.9 278.3 16.86 28.6 255.8 25.90 11.1 -355 20.2 313.5 21.46 32.3 288.1 32.96 12.5 -400 22.8 353.2 27.25 35.4 324.6 41.83 14 -450 25.6 397.5 34.42 40.9 365.4 52.85 15.6 -500 28.4 441.2 42.44 45.5 405.8 65.33 17.5 -560 31.9 494.6 53.33 50.9 454.7 81.83 19.6 -630 35.8 556.6 67.31 57.3 511.4 103.66 22.1 -

(1) The standard dimensions ration SDR corresponds to the quotient between the outside diameter and the wall thickness of the pipe. It is non-dimensional

(2) The nominal pressure PN corresponds to the maximum permissible operating pressure of the pipe at 20ºC, in bar(3) e = Minimum Wall Thickness in mm(4) Out of Roundness as per ISO 11922-1

This table is based on the standards ISO 4437 and ISO 4065/ISO 161/1.

The weights are calculated on the base of average diameter and thickness values, according to tolerance specifi ed in the standard ISO 11922-1.

POLYETHYLENE (PE)

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Composition of PVC Pipe Material

PVC is a vinyl chloride polymer and is derived from coal or oil, and salt.

The unique properties of polyvinyl chloride polymer are further enhanced by the addition of special additives to create tough, resilient and ductile compounds, which are then used in the extrusion of PVC pipes. The extrusion process itself is fi nely controlled and has a direct bearing on the fi nal properties of the product.

The pipe manufacturer’s objective is to manufacture pipe within tight dimensional tolerances at high output rates while maintaining mechanical performance characteristics. Therefore polymers for pipe extrusion are manufactured to a high degree of consistency, with an emphasis on maintaining tight control of all key properties.

The nature and volumes of additives used vary to some extent, depending on the required end result.

The essential additives used in PVC pipe and fi ttings formulations are heat stabilisers, lubricants, impact modifi ers, processing aids and pigments.

Heat stabilisers

Heat stabilisers are required to prevent decomposition of the polymer during processing and outdoor use.

Lubricants

The reason for adding lubricants is to provide good melt fl ow through the processing equipment as well as a good physical appearance.

Impact modifi ers

Impact modifi ers are added to formulations to specifi cally improve the impact strength and toughness of the pipes manufactured.

Fillers

Small amounts of fi llers are added to PVC potable water pipe formulations and have an effect on the surface fi nish and may also modify the mechanical properties of the pipe.

Pigments

As most PVC pipes are coloured, an appropriate pigment, which may have an effect on weathering and long-term mechanical performance, has to be selected on the basis of cost and performance.

Physical Properties

Polyvinyl Chloride (PVC) is a thermoplastic material and different formulations are used to obtain specifi c properties for different applications. Pipes can therefore be developed to meet the requirements of a wide variety of applications and conditions. The major part of each formulation is the PVC resin.

General (PVC-U, PVC-M, PVC-0)

The general properties given below are those for PVC formulations used in pipe manufacture. It should be noted that these properties are dependant on temperature and the duration of stress application.

PVC-U is unplasticized (Rigid) PVC and is the oldest PVC pipe technology.

PVC-M is modifi ed PVC to provide improved ductility and impact resistance.

Biaxially oriented PVC (PVC-O) pressure pipes are produced by a special process where the molecules are stretched or orientated to provide signifi cant increase is in strength and toughness.

POLYVINYL CHLORIDE (PVC)

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Physical Units PVC-U PVC-M PVC-O

Co-effi cient of linear expansion K-1 6 x 10-5 6 x 10-5 -

Density kg/m3 1.4 x 10³ 1.4 x 10³ -

Flammability (oxygen index) % 45 45 45

Shore hardness (D) 70 - 80 70 - 80 70 - 80

Softening point (Vicat - minimum) ºC 78 - 81 78 - 81 78 - 81

Specifi c heat J/kg/K 1.0 x 10³ 1.0 x 10³ 1.0 x 10³

Thermal conductivity (at 0º-50ºC) W/m/K 0.14 0.14 0.14

Mechanical

Elastic Modulus (long term - 50 years) MPa 1 500 1 400 1 800

Elastic Modulus (short term - 100 seconds) MPa 3 300 3 000 4 000

Elongation at break % 50 75 75

Poisons Ratio 0.4 0.4 0.4

Tensile strength (50 year - extrapolated) MPa 26 26 50

Tensile strength (short-term) MPa 52 48 75

Friction Factors

Manning 0.008 - 0.009 0.008 - 0.009 0.008 - 0.009

Hazen Williams 150 150 150

Nikuradse roughness (k) mm 0.03 0.03 0.03

Benefi ts

• Resistance to abrasion and scouring.

• Resistance to attack by acid or alkaline soils.

• Impervious to chemicals found in sewerage.

• Good fl ow characteristics.

• Not damaged by modern cleaning methods.

• Good impact properties, an important factor in installation, transportation and operation.

• Durability and toughness - resistance to handling and installation damage.

• Corrosion resistance - greater service life.

• Infl amable - self extinguishing.

• Lower mass - ease of handling and installation, particularly suited to labour intensive projects.

• Ease of repair.

• Elastomeric, locked-in sealing ring system - no specialist installation skills required. No power required onsite during installation.

• Service performance in excess of 100 years.

• Unique combination of properties

- Toughness.

- Stiffness.

- High Tensile and hoop strength.

- Excellent resistance of creep.

• Predictable long-term behaviour.

• Excellent strength/cost ratio.

Typical Physical Properties

POLYVINYL CHLORIDE (PVC)

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Applications for PVC Pipe Systems

PVC pressure pipes are specifi ed with confi dence in the following applications:

• Water mains and reticulation systems.

• Irrigation.

• Mining

• Industrial applications.

• Sewer effl uent control and water purifi cation.

Design

General

Once installed, PVC pressure pipes will operate effi ciently under pressure, without failure or leakage, over long periods of time while simultaneously preserving water quality.

Modifi ed PVC (PVC-M) Pressure Pipes

PVC raw material formulations used for the manufacture of PVC pressure pipes result in specifi c and controllable mechanical properties. Pipes can therefore be engineered to cater for a wide variety of applications and conditions. In particular, the toughness of PVC-M pressure pipe is enhanced by the incorporation of impact modifying additives.

The enhanced toughness results in improved resistance to crack propagation and therefore enables the use of a higher design stress, which results in signifi cantly reduced mass. The mass reduction and larger pipe bore brings about savings in energy consumed during manufacture and subsequent operation.

Biaxially Oriented (PVC-O) Pressure Pipes

The molecular orientation process is used in the manufacture of plastic products where increased strength is required. In the case of PVC-O pipes the process is one of biaxial orientation when the molecules are stretched (oriented) in both the circumferential (hoop) and axial (length) directions and thus aligned to provide strength in both directions. A small diameter, thick-walled pipe is extruded and then stretched under controlled

conditions of temperature and pressure to achieve optimum molecular orientation and improvement in strength in the two directions.

The increased resistance to internal pressure makes the product extremely well suited to pressure applications. Biaxial orientation also leads to marked increase in toughness properties.

It is this combination of strength and toughness which leads to the unique properties of PVC-O pipes. These properties provide:

• A very cost effective pressure pipe.

• Material effi ciency, giving lower pipe mass for easier handling and installation.

• Higher fl ow capacity and lower pumping costs.

• Resistance to damage during transport, handling and installation.

• High resistance to crack propagation due to layered structure.

• Very low wave celerity, thereby reducing water hammer.

• Energy effi ciency due to material effi ciency and improved fl ow capacity.

Hoop Stiffness and Creep rupture Strength

The hoop stress (from Barlow’s formula) is plotted against the time (in hours) to rupture, using log scales on both axes. The resultant creep rupture regression lines for PVC-U/M and PVC-O pressure pipes are given below at 20°C.

POLYVINYL CHLORIDE (PVC)

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Figure 1: Stress-Time Lines for PVC-4, PVC-M and PVC-0 at 20°C

PVC-O regression line as per SANS 1808-85

PVC-U and PVC-M regression lines per SANS 966-Parts 1 & 2

PVC-O design stress, SANS 1808-85 (28 MPa)

PVC-M design stress, SANS 966-2 (18 MPa)

PVC-U design stress, SANS 966-1 (12.5 MPa)

Notes

1. 20°C Regression Line

The line for PVC-U and PVC-M meets the requirements of SANS 966, (Parts 1 and 2 respectively.) while the line for PVC-O meets SANS 1808-85.

Hydrostatic Strength

The addition of modifying agents reduces the short term strength but leads to a considerable increase in toughness in PVC-M pressure pipe, especially the resistance of the material to the propagation of cracks. The 1 hour hydrostatic strength at 20°C of PVC-M is 40Mpa, compared to 42Mpa for PVC-U pipe.The failure stress of both PVC-U and PVC-M at 50 years is similar, i.e. 25 MPa.

Testing at elevated temperatures is essential for the identifi cation of ductile-brittle transitions. Should operating temperatures rise above 25°C the working pressures should be de-rated.

Impact resistance

The measurement of the impact performance under external blows is a major requirement of SANS 966-2. The ductility of PVC-M pipe is shown by the standard quality control test for impact; when impacted by masses of up to 30kg dropped from a height of 20m, there is no evidence of brittle failure as experienced with PVC-U.

POLYVINYL CHLORIDE (PVC)

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Material Specifi cationDrop

Test (m)Temperature

ºC

Mass of Striker

(kg)remark

PVC-U SANS 966-1 & SANS 966-2

2,0 23 5 Pipe must not shatter.

PVC - M SANS 966-2

20,0 23 20 Pipe must fail in ductile manner (smooth hole).

PVC-O SANS 1808-85

2,0 0 10 Pipe must not shatter.

A comparison of the impact properties of PVC-U, PVC-M and PVC-O pressure pipes tested as per SANS specifi cations is given in the following table. Example: 200mm Class 16 pipe:

Pipe Design Principles: PVC-U, PVC-M and PVC-O

Design Stress (σs) and the Long-Term Safety Factor

The design stress is defi ned as the constant stress that the pipe wall can withstand for 50 years, with a defi ned safety factor.

A safety factor or overall service (design) co-effi cient (C) is applied to take into account minor variations in pipe quality, the possibility of the occurrence of brittle failure, slight surges or fl uctuations in pressure or superimposed bending stresses or point loads on the pipe, or slight surface damage resulting during installation (refer SANS 966, SANS 1808-85 and SANS ISO 4427). Thus the safety factor is applied to account for any ‘unknown’ loading or environmental conditions.

The design stress is derived from the stress-time line (refer Figure I) which gives the minimum required strength (MRS), as follows:

σs =

Where σs - Design stress

MRS - Minimum required strength at 50 years

C - Design coeffi cient (safety factor).

- PVC-U pipes designed as per SANS 966 Part 1 have a safety factor of 2.5 for pipe diameters of 90mm and below, and 2.0 for pipe diameters 110mm and above. These safety factors relate to design stresses of 10.0 and 12.5 MPa respectively.

- PVC-M pipes designed as per sans 966-2 have a safety factor of 1.4.

- PVC-O pipes designed as per sans 1808-85 may have a design factor of 1.4 (32 mpa) or 1.6 (28 mpa)

Short-term Safety Factors

It should be noted that the short-term safety factor is much higher. In fact, the more rapid the rate of pressure increase the higher the strength exhibited by the pipe. Short-term safety factors for PVC-U, PVC-M and PVC-O are over three times the design working pressure. Thus at high pressurisation rates pipes are better able to resist the higher stress levels generated by surge.

MrSC

POLYVINYL CHLORIDE (PVC)

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Outside Diameter O.D. At Any Point Wall Thickness

Size Class eMin. eMax. eMin. eMax. eMin. eMax. Avg Id

16 20 16 16.2 15.5 16.5 1.50 1.90 12.7

20 16 20 20.2 19.5 20.5 1.50 1.90 16.7

20 20 20.2 1.90 2.30 15.9

25 12 25 25.2 24.5 25.5 1.50 1.90 21.7

16 25 25.2 1.90 2.30 20.9

20 25 25.2 2.30 2.80 20

32 9 32 32.2 31.5 32.5 1.50 1.90 28.7

12 32 32.2 1.80 2.20 28.1

16 32 32.2 2.40 2.90 26.8

20 32 32.2 2.90 3.40 25.8

40 6 40 40.2 39.5 40.5 1.50 1.90 36.7

9 40 40.2 1.80 2.20 36.1

12 40 40.2 2.30 2.90 34.9

16 40 40.2 3.00 3.60 33.5

20 40 40.2 3.70 4.30 32.1

50 6 50 50.2 49.4 50.6 1.80 2.20 46.1

9 50 50.2 2.20 2.70 45.2

12 50 50.2 2.80 3.30 44

16 50 50.2 3.70 4.30 42.1

20 50 50.2 4.60 5.30 40.2

63 6 63 63.2 62.2 63.8 1.90 2.30 58.9

9 63 63.2 2.70 3.20 57.2

12 63 63.2 3.60 4.20 55.3

16 63 63.2 4.70 5.50 52.9

20 63 63.2 5.80 6.40 50.9

75 4 75 75.2 74.1 75.9 1.50 1.90 71.7

6 75 75.2 2.20 2.70 70.2

9 75 75.2 3.20 3.80 68.1

12 75 75.2 4.30 5.20 65.6

16 75 75.2 5.60 6.50 63

20 75 75.2 6.90 8.00 60.2

90 4 90 90.3 88.9 91.1 1.80 2.30 86.05

6 90 90.3 2.70 3.20 84.25

9 90 90.3 3.90 4.50 81.75

12 90 90.3 5.10 5.90 79.15

16 90 90.3 6.70 7.60 75.85

20 90 90.3 8.20 9.50 72.45

110 4 110 110.3 108.6 111.4 2.20 2.70 105.25

6 110 110.3 2.60 3.10 104.45

9 110 110.3 3.90 4.50 101.75

12 110 110.3 5.10 5.90 99.15

16 110 110.3 6.70 7.60 95.85

20 110 110.3 8.20 9.50 92.45

25 110 110.3 10.00 11.60 88.55

Pipe Dimensions

TABLE 1: SABS 966 -1:2010

POLYVINYL CHLORIDE (PVC)

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56 SAPPMA TECHNICAL MANUAL | jANUAry 2011 | 3rd Edition

POLYVINYL CHLORIDE (PVC)

Outside Diameter O.D. At Any Point Wall Thickness

Size Class eMin. eMax. eMin. eMax. eMin. eMax. Avg Id

125 4 125 125.3 123.5 126.5 2.50 3.00 119.65

6 125 125.3 3.00 3.60 118.55

9 125 125.3 4.40 5.10 115.65

12 125 125.3 5.80 6.70 112.65

16 125 125.3 7.60 8.80 108.75

20 125 125.3 9.30 10.50 105.35

25 125 125.3 11.40 13.20 100.55

140 4 140 140.4 138.3 141.7 2.8 3.30 134.1

6 140 140.4 3.30 3.90 133

9 140 140.4 4.90 5.70 129.6

12 140 140.4 6.50 7.50 126.2

16 140 140.4 8.50 9.80 121.9

20 140 140.4 10.40 12.00 117.8

25 140 140.4 12.80 14.80 112.6

160 4 160 160.4 158 162 3.20 3.80 153.2

6 160 160.4 3.80 4.40 152

9 160 160.4 5.60 6.50 148.1

12 160 160.4 7.40 8.60 144.2

16 160 160.4 9.70 11.20 139.3

20 160 160.4 11.90 13.70 134.6

25 160 160.4 14.60 16.80 128.8

200 4 200 200.5 197.6 202.6 3.90 4.70 191.65

6 200 200.5 4.70 5.50 190.05

9 200 200.5 7.00 8.10 185.15

12 200 200.5 9.20 10.70 180.35

16 200 200.5 12.10 14.00 174.15

20 200 200.5 14.90 17.20 168.15

25 200 200.5 18.20 21.00 161.05

250 4 250 250.6 247 253 4.90 5.70 239.7

6 250 250.6 5.90 6.70 237.7

9 250 250.6 8.70 6.80 234.8

12 250 250.6 11.50 13.30 225.5

16 250 250.6 15.10 17.40 217.8

20 250 250.6 18.60 21.40 210.3

25 250 250.6 22.80 26.30 201.2

315 4 315 315.6 311.2 318.8 6.20 7.20 301.9

6 315 315.6 7.40 8.60 299.3

9 315 315.6 11.00 12.70 291.6

12 315 315.6 14.50 16.70 284.1

16 315 315.6 19.00 21.90 274.4

355 4 355 355.7 350.7 359.3 7.00 8.10 340.25

6 355 355.7 8.40 9.70 337.25

9 355 355.7 12.40 14.30 328.65

12 355 355.7 16.30 18.80 320.25

16 355 355.7 21.40 24.70 309.25

400 4 400 400.7 395.2 404.8 7.80 10.00 382.55

6 400 400.7 9.40 10.90 380.05

9 400 400.7 14.00 16.20 370.15

12 400 400.7 18.40 21.20 360.75

16 400 400.7 24.10 27.80 348.45

450 4 450 450.8 445.1 454.9 8.90 10.30 431.2

6 450 450.8 10.60 12.20 427.6

9 450 450.8 15.70 18.10 416.6

12 450 450.8 20.70 23.90 405.8

500 4 500 500.9 494 506 9.80 11.30 479.35

6 500 500.9 11.80 13.60 475.05

9 500 500.9 17.40 20.10 462.95

12 500 500.9 22.90 26.40 451.15

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57SAPPMA TECHNICAL MANUAL | jANUAry 2011 | 3rd Edition

TABLE 2: SABS 966 - 2

POLYVINYL CHLORIDE (PVC)

Outside Diameter O.D. At Any Point Wall Thickness

Size Class eMin. eMax. eMin. eMax. eMin. eMax. Avg Id

50 6 50 50.2 49.4 50.6 1.50 1.90 46.7

9 50 50.2 1.50 1.90 46.7

12 50 50.2 1.70 2.10 46.3

16 50 50.2 2.20 2.70 45.2

20 50 50.2 2.70 3.20 44.2

25 50 50.2 3.30 3.90 42.9

63 6 63 63.2 62.2 63.8 1.50 1.90 59.7

9 63 63.2 1.60 2.00 59.5

12 63 63.2 2.10 2.60 58.4

16 63 63.2 2.70 3.20 57.2

20 63 63.2 3.40 4.00 55.7

25 63 63.2 4.10 4.80 54.2

75 6 75 75.2 74.1 75.9 1.50 1.90 71.7

9 75 75.2 1.90 2.30 70.9

12 75 75.2 2.50 3.00 69.6

16 75 75.2 3.20 3.80 68.1

20 75 75.2 4.00 4.70 66.4

25 75 75.2 4.90 5.70 64.5

90 6 90 90.3 88.9 91.1 1.80 2.20 86.15

9 90 90.3 2.20 2.70 85.25

12 90 90.3 3.00 3.60 83.55

16 90 90.3 3.90 4.50 81.75

20 90 90.3 4.80 5.60 79.75

25 90 90.3 5.90 6.80 77.45

110 6 110 110.3 108.6 111.4 2.20 2.70 105.25

9 110 110.3 2.70 3.20 104.25

12 110 110.3 3.60 4.20 102.35

16 110 110.3 4.70 5.50 99.95

20 110 110.3 5.80 6.70 97.65

25 110 110.3 7.20 8.30 94.65

122 6 122 122.3 120.6 123.4 2.40 2.90 116.85

9 122 122.3 3.00 3.60 115.55

12 122 122.3 4.00 4.70 113.45

16 122 122.3 5.20 6.00 110.95

20 122 122.3 6.50 7.50 108.15

25 122 122.3 8.00 9.20 104.95

125 6 125 125.3 123.5 126.5 2.50 3.00 119.65

9 125 125.3 3.10 3.70 118.35

12 125 125.3 4.10 4.80 116.25

16 125 125.3 5.40 6.30 113.45

20 125 125.3 6.60 7.60 110.95

25 125 125.3 8.20 9.50 107.45

140 6 140 140.4 138.3 141.7 2.80 3.30 134.1

9 140 140.4 3.50 4.10 132.6

12 140 140.4 4.60 5.30 130.3

16 140 140.4 6.00 7.00 127.2

20 140 140.4 7.40 8.60 124.2

25 140 140.4 9.10 10.50 120.6

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58 SAPPMA TECHNICAL MANUAL | jANUAry 2011 | 3rd Edition

POLYVINYL CHLORIDE (PVC)

Outside Diameter O.D. At Any Point Wall Thickness

Size Class eMin. eMax. eMin. eMax. eMin. e Max. Avg Id

160 6 160 160.4 158 162 3.20 3.90 153.1

9 160 160.4 4.00 4.70 151.5

12 160 160.4 5.20 6.00 149

16 160 160.4 6.90 8.00 145.3

20 160 160.4 8.50 9.80 141.9

25 160 160.4 10.40 12.00 137.8

177 6 177 177.5 175 179 3.50 4.10 169.65

9 177 177.5 4.40 5.10 167.75

12 177 177.5 5.80 6.70 164.75

16 177 177.5 7.70 8.90 160.65

20 177 177.5 9.40 10.90 156.95

25 177 177.5 11.50 13.30 152.45

200 6 200 200.5 197.6 202.6 3.90 4.40 191.95

9 200 200.5 4.90 5.70 189.65

12 200 200.5 6.50 7.50 186.25

16 200 200.5 8.60 9.90 181.75

20 200 200.5 10.60 12.30 177.35

25 200 200.5 13.00 15.00 172.25

250 6 250 250.6 247 253 4.90 5.70 239.7

9 250 250.6 6.10 7.10 237.1

12 250 250.6 8.10 9.40 232.8

16 250 250.6 10.70 12.40 227.2

20 250 250.6 13.20 15.20 221.9

25 250 250.6 16.30 18.80 215.2

315 6 315 315.6 311.2 318.8 6.20 7.20 301.9

9 315 315.6 7.70 8.90 298.7

12 315 315.6 10.20 11.80 293.3

16 315 315.6 13.50 15.60 286.2

20 315 315.6 16.60 19.10 279.6

355 6 355 355.7 350.7 359.3 7.00 8.10 340.25

9 355 355.7 8.70 10.10 336.55

12 355 355.7 11.50 13.30 330.55

16 355 355.7 15.20 17.50 322.65

20 355 355.7 18.70 21.60 315.05

400 6 400 400.7 395.2 404.8 7.80 9.00 383.55

9 400 400.7 9.80 11.30 379.25

12 400 400.7 13.00 15.00 372.35

16 400 400.7 17.10 19.70 363.55

20 400 400.7 21.10 24.30 354.95

450 6 450 450.8 445.1 454.9 8.90 10.30 431.2

9 450 450.8 11.00 12.70 426.7

12 450 450.8 14.60 16.80 419

16 450 450.8 19.20 22.10 409.1

20 450 450.8 23.70 27.30 399.4

500 6 500 500.9 494 506 9.80 11.30 479.35

9 500 500.9 12.20 14.10 474.15

12 500 500.9 16.20 18.70 465.55

16 500 500.9 21.30 24.50 454.65

20 500 500.9 26.40 30.40 443.65

TABLE 2: SABS 966 - 2 continued

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59SAPPMA TECHNICAL MANUAL | jANUAry 2011 | 3rd Edition

Outside Diameter O.D. At Any Point Wall Thickness

Size Class eMin. eMax. eMin. eMax. eMin. eMax. Avg Id

40 N/A 40 40.2 39.5 40.5 2.00 2.40 36

50 N/A 50 50.2 49.4 50.6 2.20 2.60 45

75 N/A 75 75.3 74.1 75.9 3.20 3.80 68

110 N/A 110 110.3 108.6 111.4 3.20 3.80 103

160 N/A 160 160.4 158 162 3.30 3.90 153

Outside Diameter O.D. At Any Point Wall Thickness

Size Class eMin. eMax. eMin. eMax. eMin. eMax. Avg Id

110 ND 110 110.3 108.6 111.4 2.20 2.80 105

HD 110 110.3 3.00 3.50 104

160 ND 160 160.4 158 162 3.20 3.80 153

HD 160 160.4 4.70 5.40 150

200 ND 200 200.5 197.6 202.6 3.90 4.50 192

HD 200 200.5 5.90 6.70 188

250 ND 250 250.5 247 253 5.00 5.70 240

HD 250 250.5 7.30 8.30 235

315 ND 315 315.6 311.2 318.8 6.20 7.10 302

HD 315 315.6 9.20 10.40 296

400 ND 400 400.7 395.2 404.8 7.90 8.90 384

HD 400 400.7 11.70 13.10 376

500 ND 500 500.9 494 506 9.80 11.00 480

HD 500 500.9 14.60 16.30 470

TABLE 4: SABS 1283 12,5 mpa

TABLE 3: SABS 967 & 791

POLYVINYL CHLORIDE (PVC)

Outside Diameter O.D. At Any Point Wall Thickness

Size Class eMin. eMax. eMin. eMax. eMin. eMax. Avg Id

105 6 105 105.3 103.9 106.1 2.50 2.90 99.75

9 105 105.3 3.70 4.20 97.25

12 105 105.3 4.80 5.50 94.85

16 105 105.3 6.40 7.20 91.55

20 105 105.3 7.80 8.70 88.65

25 105 105.3 9.50 10.60 85.05

110 6 110 110.3 108.6 111.4 2.60 3.00 104.55

9 110 110.3 3.90 4.40 101.85

12 110 110.3 5.10 5.80 99.25

16 110 110.3 6.70 7.50 95.95

20 110 110.3 8.20 9.20 92.75

25 110 110.3 10.00 11.20 88.95

125 6 125 125.3 123.5 126.5 3.00 3.50 118.65

9 125 125.3 4.40 5.00 115.75

12 125 125.3 5.80 6.50 112.85

16 125 125.3 7.60 8.50 109.05

20 125 125.3 9.30 10.40 105.45

25 125 125.3 11.40 12.80 100.95

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60 SAPPMA TECHNICAL MANUAL | jANUAry 2011 | 3rd Edition

SABS 1283 12,5 mpa (continued)

POLYVINYL CHLORIDE (PVC)

Outside Diameter O.D. At Any Point Wall Thickness

Size Class eMin. eMax. eMin. eMax. eMin. eMax. Avg Id

140 6 140 140.4 138.3 141.7 3.30 3.80 133.1

9 140 140.4 4.90 5.50 129.8

12 140 140.4 6.50 7.30 126.4

16 140 140.4 8.50 9.50 122.2

20 140 140.4 10.40 11.60 118.2

25 140 140.4 12.80 14.20 113.2

155 6 155 155.4 153.1 156.9 3.60 4.10 147.5

9 155 155.4 5.40 6.10 143.7

12 155 155.4 7.10 8.00 140.1

16 155 155.4 9.40 10.50 135.3

20 155 155.4 11.50 12.80 130.9

25 155 155.4 14.10 15.70 125.4

160 6 160 160.4 158 162 3.80 4.30 152.1

9 160 160.4 5.60 6.30 148.3

12 160 160.4 7.40 8.30 144.5

16 160 160.4 9.70 10.80 139.7

20 160 160.4 11.90 13.20 135.1

25 160 160.4 14.60 16.20 129.4

200 6 200 200.4 197.6 202.6 4.70 5.30 190.2

9 200 200.4 7.00 7.90 185.3

12 200 200.4 9.20 10.30 180.7

16 200 200.4 12.10 13.50 174.6

20 200 200.4 14.90 16.50 168.8

25 200 200.4 18.20 20.20 161.8

210 6 210 210.4 207.5 212.7 5.00 5.70 199.5

9 210 210.4 7.30 8.20 194.7

12 210 210.4 9.70 10.80 189.7

16 210 210.4 12.70 14.40 183.1

20 210 210.4 15.60 17.30 177.3

25 210 210.4 19.10 21.20 169.9

225 6 225 225.5 222.8 227.2 5.30 6.00 213.95

9 225 225.5 7.90 8.80 208.55

12 225 225.5 10.30 11.50 203.45

16 225 225.5 13.60 15.10 196.55

20 225 225.5 16.70 18.50 190.05

25 225 225.5 20.50 22.70 182.05

250 6 250 250.5 247 253 5.90 6.60 237.75

9 250 250.5 8.70 9.70 231.85

12 250 250.5 11.50 12.80 225.95

16 250 250.5 15.10 16.80 218.35

20 250 250.5 18.60 20.60 211.05

25 250 250.5 22.80 25.20 202.25

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61SAPPMA TECHNICAL MANUAL | jANUAry 2011 | 3rd Edition

TABLE 5: SABS 1283 10 mpa

SABS 1283 12,5 mpa (continued)

POLYVINYL CHLORIDE (PVC)

Outside Diameter O.D. At Any Point Wall Thickness

Size Class eMin. eMax. eMin. eMax. eMin. eMax. Avg Id

315 6 315 315.6 311.2 318.8 7.40 8.30 299.6

9 315 315.6 11.00 12.20 292.1

12 315 315.6 14.50 16.10 284.7

16 315 315.6 19.00 21.10 275.2

355 6 355 355.7 352 358 8.40 9.40 337.55

9 355 355.7 12.40 13.80 329.15

12 355 355.7 16.30 18.10 320.95

16 355 355.7 21.40 23.70 310.25

400 6 400 400.7 396.8 403.2 9.40 10.50 380.45

9 400 400.7 14.00 15.60 370.75

12 400 400.7 18.40 20.50 361.45

16 400 400.7 24.10 26.70 349.55

450 6 450 450.8 446.6 453.4 10.60 11.80 428

9 450 450.8 15.70 17.40 417.3

12 450 450.8 20.70 22.90 406.8

500 6 500 500.9 496.4 503.6 11.80 13.10 475.55

9 500 500.9 17.40 19.30 463.75

12 500 500.9 22.90 25.50 452.05

Outside Diameter O.D. At Any Point Wall Thickness

Size Class eMin. eMax. eMin. eMax. eMin. eMax. Avg Id

55 4 55 55.2 54.4 55.6 1.50 1.80 51.8

6 55 55.2 1.60 1.90 51.6

9 55 55.2 2.40 2.80 49.9

12 55 55.2 3.20 3.70 48.2

16 55 55.2 4.10 4.70 46.3

90 4 90 90.3 88.9 91.1 1.80 2.10 86.25

6 90 90.3 2.70 3.10 84.35

9 90 90.3 3.90 4.40 81.85

12 90 90.3 5.10 5.80 79.25

16 90 90.3 6.70 7.50 75.95

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62 SAPPMA TECHNICAL MANUAL | jANUAry 2011 | 3rd Edition

Strength and Toughness

PVC-M Pressure Pipes

The stress-time lines for PVC-U, PVC-M and PVC-O are related to the strength properties of these materials. However, strong materials are not necessarily tough and in many cases can be quite brittle. The best example is glass which, in its purest form, is extremely strong but by the introduction of a small defect or notch becomes very brittle indeed. This is due to the high stresses that are developed at the tip of the notch which leads to unstable crack growth. In the case of engineering materials, especially those used for pipes, in addition to strength and stiffness, a major requirement is toughness since it is this property that increases the resistance of the material to the propagation of cracks.

The E modulus of PVC-U is almost three times that of PE but, because of its higher susceptibility to brittle failure, this cannot be fully exploited. Thus, based on the widely used safety factors of 2,0 and 1,25 respectively for PVC-U and HPDE, the wall thickness of PVC-U is only about 50% that of the equivalent PE (PE 80) pipe and not 33% as it would be purely on a strength basis.

The reason for the relatively large safety factor with PVC-U against that of PE is the result of the greater ductility of polyethylene. Larger safety factors are normally a requirement of materials having greater strength, but perceived to be more brittle.

In the development of PVC-M advantage was taken of many years of work on the science and technology of alloys and blends, the objective being to develop a material with the long-term strength of PVC-U along

with the toughness of polyethylene. The excellent long-term strength properties of PVC-U have been retained while the toughness of the material has been enhanced by the incorporation of impact modifi ers which, even in relatively small amounts, signifi cantly change the characteristics of the pipe such that a completely ductile failure mode may be achieved in the fracture toughness, high speed impact and other tests as per SANS 966 Part 2.

PVC-M pressure pipe is produced so as to have the optimum balance between strength and toughness, which allows the material to survive point loads, for example, without embrittlement or loss in pressure carrying capacity.

The higher safety factors used in the design of PVC-U pipes are not necessary with tough materials such as PVC-M since this material’s failure mode is dominated by ductile yielding. The safety factor for PVC-M is 1.4 and a design stress of 18 MPa is used to calculate the wall thickness according to Barlow’s formula:

e = p.de 2σs+ p

where e - minimum wall thickness (mm)

p - maximum operating pressure (MPa)

de - mean external diameter (mm)

σs - design stress (MPa)

The improved material effi ciency and hydraulic capacity give signifi cant life cycle energy savings.

POLYVINYL CHLORIDE (PVC)

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63SAPPMA TECHNICAL MANUAL | jANUAry 2011 | 3rd Edition

Thus, in addition to strength, toughness is the other important property of plastic pipe materials. PVC-O is unique in that it has both very high strength and high toughness. Long-term pipeline performance is dependent on both these properties. Toughness can be defi ned as resistance to impact and resistance to crack growth, ie. toughness prevents cracks from starting (initiation) and also prevents the transfer (propagation) of cracks through the pipe wall. Cracks or notches may be initiated during handling or installation and result in stress concentration effects in the pipe which can eventually result in failure. It is the toughness properties of PVC-O which prevents this common cause of pipeline failure.

The superior toughness properties arise from the biaxial orientation of the molecules which gives a layered or laminar structure.

Given the outstanding strength and toughness properties, a 50 year safety factor of 1,6 can be applied for MRS 45 PVC-O materials, as specifi ed in SANS 1808-85. Design stress of 28 MPa is used for these PVC-O pipes resulting in material savings of over 50% and 30% against the equivalent PVC-U and PVC-M products, respectively.

Advantages of PVC-O pipes which relate to the higher design stress are increased hydraulic capacity and improved handling and installation characteristics. The greater fl ow capacity of PVC-O pipes provide greater energy savings and thus have less effect on the environment than other pipe materials, including traditional materials such as ductile iron.

Pressure Variation and Surge Pressures

The stress regression lines are derived using constant stresses; in pipelines the stress on the material is rarely constant, varying as the pressure varies and as superimposed loads vary.

The latter usually stabilise fairly quickly, at least within the fi rst year of the network life, but pressure variations are there forever. As with any other pipe material, due allowance for this must be made in designing a water reticulation network with PVC pipes. Anti-surge devices such as air vessels, non-return valves, programmed use

of pumps etc, should be incorporated where necessary. Lower surge pressures develop in PVC pipes as a result of lower surge wave velocities and this has enabled PVC pipes to be used in areas where water hammer has caused pipes manufactured from other materials to fracture. Above all, it enables one to operate with lower pressure classes for PVC.

Considerable research has been done on the fatigue properties of plastic pipelines. Recently work has been published on fatigue properties of PVC-M related to actual site conditions in water distribution systems. It is concluded that PVC-M pipes will not fail under conditions of dynamic and static stress within 50 years provided the total stress does not exceed 17,5MPa and the stress amplitude over one million pressure cycles (equal to 55 cycles per day for 50 years) is below 3,0MPa

Effect of Temperature Change

Working Pressure

20°C is the standard design temperature for PVC pipes and rated working pressures are usually quoted for this temperature. PVC pressure pipe functions perfectly well below 20°C right down to freezing point and can in fact, withstand higher pressures than those quoted at 20°C.

Above 20°C, working pressures must be down-rated if the same factors of safety are to be held. The following reduction factors should be applied:

Working Temperature (°C)

Multiplication Factors

20 1.0

30 0.9

40 0.7

50 0.5

60 0.3

It should be noted that PVC-O pipes cannot be used at operating temperatures above 45°C .

POLYVINYL CHLORIDE (PVC)

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64 SAPPMA TECHNICAL MANUAL | jANUAry 2011 | 3rd Edition

Sub Zero Temperatures

Water has been known to freeze in PVC pipes without causing fractures, but permanent strain can result, leading to severe reduction in the working life of the pipe. Hence PVC pipes – like other pipes – should be protected against sub zero temperatures.

Expansion and Contraction

All plastics have high co-effi cients of expansion and contraction, several times those of metals. This must be allowed for in any installation by the use of expansion joints, expansion loops etc.

MaterialCo-effi cient of

expansion mm/mºC

PVC 0,08

PE 0,2

Steel 0,012

Copper 0,02

Ultra Violet resistance

Most plastics are affected by U.V. light. PVC pressure pipes have pigments and light stabilisers incorporated in their formulations and if pressure pipes have to be exposed for an indefi nite period, they should be painted, preferably with one coat of white alkyd enamel or PVA, or suitable covering should be provided. Paint containing solvent thinners should be avoided.

POLYVINYL CHLORIDE (PVC)

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65SAPPMA TECHNICAL MANUAL | jANUAry 2011 | 3rd Edition

Physical Properties of Polypropylene (PP)

Typical Value Unit Test Method

Density 905 kg/m3 ISO 1183

Melt Flow rate (230oC/2.16kg) 0.30 g/10 min ISO 1133

Melt Flow rate (190oC/5.0kg) 0.50 g/10 min ISO 1133

Tensile Stress at yield

(50 mm/min) 30 MPa ISO 527-2

Tensile Strain at yield (50 mm/min) 10 % ISO 527-2

Tensile Modulus (1 mm/min) 1300 MPa ISO 527

Charpy Impact Strength, notched

(+23oC) 50 kJ/m2 ISO 179/1eA

Charpy Impact Strength, notched

(-20oC) 5 kJ/m2 ISO 179/1eA

Vicat Softening Temperature

B (50 N) 91 oC ISO 306

Heat defl ection Temperature

(HDT) 96 oC ISO 75 B

Benefi ts & Specifi cations

The major benefi t of Polypropylene pipe is related to its ability to withstand higher operating temperatures (up to 95oC for water) than PE or PVC. In addition PP is also resistant to a very wide range of corrosive chemicals and is therefore a very suitable material for most industrial applications.

Suitable polymer for large diameter pressure pipe is not produced locally and has to be imported.

Typically this would be a propylene homo-polymer with high molecular weight, low melt fl ow and fi nely

grained crystalline structure, giving it excellent impact strength even at low temperatures, as well as increased hydrostatic strength and improved chemical resistance. The colour is usually ivory grey.

PR-R (Polypropylene Random) is increasingly used in hot and cold water systems and has excellent impact properties at low and high temperatures. The color is typical blue, green or brown.

Major applications include hot industrial effl uents, plumbing, under fl oor heating and other industrial-chemical installations.

POLYPROPYLENE (PP)

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66 SAPPMA TECHNICAL MANUAL | jANUAry 2011 | 3rd Edition

Polyethylene Welding Processes

General

There are fi ve stages in the welding process, namely

a) bead-forming (also known as adapting),

b) heating (also known as soaking or pre-heating),

c) changeover (also known as conversion),

d) joining

e) cooling.

These stages are represented in fi gure 3.

The principle of heated-tool butt welding is illustrated in fi gure 4.

To ensure that the pipe walls remain at a constant ambient temperature, the open ends of the pipes may be closed off before welding to prevent airfl ow through the pipe, which could cause uneven temperatures and too rapid cooling of the weld.

SANS 10268-1:2009Edition 1.3

Figure 3 — Pressure/time diagram

Bead-forming

The heated tool, heated to the predetermined temperature, is inserted between the joint faces to be joined and the joint faces are pressed against the heated tool under the force or pressure setting for bead-forming. The force or pressure is maintained until the full joint faces of the pipes are in contact with the heated tool and a bead is formed around the circumference of both pipe components at the contact face (see column 2 of table 2).

Heating or soaking

The welding pressure setting for heating is reduced to 0,01 N/mm2 during the heating or soaking period.

Changeover

After the heating or soaking time has expired, the joint faces are withdrawn from the heating tool, which is either swung out of the way or removed and placed in a holding bin. The heating plate shall be removed without damage to, or contamination of the joint faces. The joint faces are then immediately pressed together. (See table 2 for changeover times, which must be kept to a minimum to prevent cooling of the molten plastics.)

POLYETHYLENE JOINTING SYSTEMS

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67SAPPMA TECHNICAL MANUAL | jANUAry 2011 | 3rd Edition

Table 2 — Recommended values for the heated-tool welding of high-density polyethylene (PE-HD), determined at an ambient temperature of 20 °C and at moderate airfl ow

1 2 3 4 5 6

Nominal wallthickness

mm

Bead-formingρ = 0,15 N/mm2

Height of beadprior to heating

period(min. values)

mm

Heatingρ < 0,02 N/mm2

Heating timea

s

ChangeoverJoining

ρ = 0,15 to 0,20 N/mm2

Maximumtime

s

Time tocompletepressurebuild-up

s

Total coolingtime while

under joiningpressure

min

Up to 4,5

4,5 to 7

7 to 12

12 to 19

19 to 26

26 to 37

37 to 50

50 to 70

0,5

1,0

1,5

2,0

2,5

3,0

3,5

4,0

45

45 to 70

70 to 120

120 to 190

190 to 260

260 to 370

370 to 500

500 to 700

5

5 to 6

6 to 8

8 to 10

10 to 12

12 to 16

16 to 20

20 to 25

5

5 to 6

6 to 8

8 to 11

11 to 14

14 to 19

19 to 25

20 to 35

6

6 to 10

10 to 16

16 to 24

24 to 32

32 to 45

45 to 60

60 to 80

a For PE-HD, the heating time, in seconds, is approximately 10 times the wall thickness, in millimetres.

NOTE Less than wall thickness 4,5 mm will result in an increase in the risk factor for weld failure and care should be taken with regard to the substance being carried by the completed installation. If the installation is to carry dangerous substances, other welding methods should be considered.

b) Heated-tool temperature as a function of pipe wall thickness for polyethylene (PE-HD)

Figure 1 — Heated-tool temperature as a function of pipe wall thickness for polyethylene (PE-HD)

POLYETHYLENE JOINTING SYSTEMS

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68 SAPPMA TECHNICAL MANUAL | jANUAry 2011 | 3rd Edition

SANS 10268-1:2009Edition 1.3

Figure 4 — Principle of heated-tool butt welding

joining

When the components to be welded have been brought into contact with each other, the joining force or pressure shall be continuously and evenly increased from zero to the fi nal value indicated in table 2. This increase shall occur within the time frame indicated in the table that is used, and the fi nal pressure shall be maintained until the weld has cooled. The bead will attain its fi nal shape during this time. Fast cooling or the use of coolants will severely affect the weld quality and are therefore forbidden. A uniform bead shall be present inside and outside the pipe at the joint as indicated in fi gure 5. In the case of larger pipes of wall thickness 20 mm or more, covering the weld zone during cooling to slow the cooling process will have a benefi cial effect on the weld quality. Uneven bead formation might be caused by uneven fl ow behaviour of the materials being joined.The established height K (see fi gure 5) of the bead shall always exceed zero.

SANS 10268-1:2009Edition 1.3

Figure 5 — Bead formation

Testing and approval

For testing of the fi nished welds, see SANS 6269.For approval of welders, see SANS 10269.For approval of welding procedures, see SANS 10270.

Heated-tool socket welding

Principle

Heated-tool socket welding is a variant of heated-tool butt welding, except that the heating tool is made up of a socket on one side and a spigot on the other side. The pipe to be welded is inserted into the socket while the fi tting is placed over the spigot. When heating has been completed, the heating tool is withdrawn and the two components are pushed one into the other and held under pressure until cool. This method of joining is used for semi-crystalline materials such as polyvinylidene fl uoride (PVDF), polyethylene (PE) and polypropylene (PP). Manual welding may be undertaken with pipes of diameter up to and including 50 mm, but above this diameter, a welding machine is required to obtain the necessary pressure to ensure a good joint. When large numbers of joints in the smaller diameters are required, production effi ciency is increased if a welding machine is used. In heated-tool socket welding, the welding temperature is much higher than in heated-tool butt welding (between 250 °C and 270 °C), since no pre-heating takes place. The heating tool has to be treated with a non-stick coating such as PTFE to prevent adhesion to the molten plastics components. See ISO 8085-1 and ISO 8085-2 for the pipe-fi tting specifi cations. Figure 6 illustrates the principle of heated-tool socket welding.

POLYETHYLENE JOINTING SYSTEMS

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SANS 10268-1:2009Edition 1.3

Figure 6 — Principle of heated-tool socket welding

The pipe components to be joined and the heating tool are fi rst axially aligned, after which the pipe and the fi tting are moved into and onto the heated tool and held there for the specifi ed time in accordance with table 6 and 7 (depending on the material being welded). They are then withdrawn from the tool, which is rapidly moved out of the way. The pipe and fi tting are then brought together and held under pressure for the specifi ed time in accordance with table 6 and 7.

SANS 10268-1:2009Edition 1.3

Table 5 — Pipe chamfering

Dimensions in millimetres

1 2 3 4

Pipe diameterd

Pipe peelingdiameter

Insertiondepth

l

Pipechamfer

b16 15,90 ± 0,05 13 2

20 19,90 ± 0,05 14 2

25 24,90 ± 0,05 15 2

32 31,90 ± 0,05 17 2

40 39,85 ± 0,10 18 2

50 49,85 ± 0,10 20 2

63 62,80 ± 0,15 26 3

75 74,80 ± 0,15 29 3

90 89,80 ± 0,15 32 3

110 109,75 ± 0,20 35 3

Execution of the weld

Manual welding

The fi tting is pushed onto the heated spigot and the pipe is inserted into the heated socket up to amark previously made. The components are retained on the heating tool for the heating timespecifi ed in table 6 and 7 (depending on the material being welded).

After expiration of the heating time, the components are sharply withdrawn from the heating tool and, without any twisting motion, are pushed together up to the mark on the pipe. Table 6 and 7 (depending on the material being welded) give the maximum permissible changeover periods. The components shall be held in this position without any movement for the period indicated in table 6 and 7 (depending on the material being welded) to allow the joint to cool before stress loads can be applied. The end of the pipe shall not touch the shoulder inside the socket. A weld upset or bead shall be present over the entire circumference of the joint. If the bead is not present, the weld is not acceptable.

After every weld has been completed, the heating tool shall be allowed to cool to a safe temperature and shall be cleaned with cleaning solvent and lint-free paper.

Welding with a welding machine

The basic principles are the same as for manual welding, except that the components are held in clamping devices that can be moved in a horizontal direction to bring the components up to the heating tool, to withdraw them from the heating tool (which is then swung out of the way), and to press the pipe into the fi tting once fusion temperature has been reached. Before welding starts, the axial alignment of the clamping devices shall be checked, and the movement stops that are set up to control the insertion depth of the pipe into the fi tting shall also be checked. All other details concerning welding temperature, heating, changeover and cooling times are contained in table 6 and 7 (depending on the material being welded).

POLYETHYLENE JOINTING SYSTEMS

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SANS 10268-1:2009Edition 1.3

Table 6 — Recommended values for the heated-tool socket welding of pipeline components of polypropylene (PP) at an ambient temperature of 20 °C and at moderate airfl ow

1 2 3 4 5Outside pipe

cooling timesmm

Minimum pipe wall thickness

mm

Heatingtime

s

Changeover time (maximum)

s

Coolingmin.

152025324050637590110

2,02,52,73,03,74,63,64,35,16,3

5578121824304050

44466688810

2224446668

Table 7 — Recommended values for the heated-tool socket welding of pipeline components of high-density polyethylene (PE-HD) at an ambient temperature of 20 °C and at moderate airfl ow

1 2 3 5 6Outside pipe

diameter

mm

Heating times

Changeovertime

(maximum)s

Joining and Cooling Times

For PN10SDR 11a

For PN 6SDR 17,666a

Joinings

Coolingmm

162025324050637590110125

557812122430405060

––b

b

b

b

b

15223035

4446668881010

66101020203030405060

22244466688

a Standard dimension ratio of nominal diameter to wall thickness.

b Not recommended because of insuffi cient wall thickness.

POLYETHYLENE JOINTING SYSTEMS

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Welder Training and Qualifi cations

Welders need to be trained by a recognised institution in one of the following welding processes:

Butt-welding (HS) Socket fusion welding (HS) Electro fusion welding (HM) Hot-gas extrusion welding (WE)

Ensure the welder is trained for the process being specifi ed. PFSA training course are currently the only nationally recognised thermal welder training course and is registered through Merseta.

On successful completion of the training course the welder is tested in accordance with SANS 10269 – Testing and approval of welders.

A certifi cate is issued indicating the welding process the welder is found to be competent in. Welders that do not achieve a min. of 70% in the theoretical exam may only weld under supervision of a fully qualifi ed welder. (see annexure) Beware that there are dubious characters out there that will fraudulently manipulate certifi cates, please check their legitimacy with PFSA. IFPA members only make use of certifi ed welders that has gained appropriate experience.

POLYETHYLENE JOINTING SYSTEMS

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72 SAPPMA TECHNICAL MANUAL | jANUAry 2011 | 3rd Edition

Welding - Equipment

Minimum standards as per SANS 1671-

PART 1: Heated Tool Welding

PART 2: Electro fusion Welding

PART 3: Hot Gas Welding

PART 4: Hot Gas Extrusion Welding

PART 5: Solvent Welding

Quality Control - Pre-Installation: Sample welds to be performed and bend tests performed i.a.w. SANS 6269 Paragraph 7.2 Ensure welding equipment gauges e.g. pressure gauges and temperature gauges are calibrated. Refer to SANS 10268-10 Weld defects to be used as a guide for visual inspection.

Destructive Test

Procedure

Unless otherwise agreed upon or specifi ed in the terms of delivery for the product to be tested, the test shall be carried out at an ambient temperature of 23 °C ± 2 °C. The test specimen and testing equipment shall be set up as shown in fi gure 5.

Figure 5 — Diagram of the mechanical test

The speed of testing shall be in accordance withtable 7.

Table 7 — Bending test speedsfor relevant thermoplastics

1 2

MaterialTest speedmm/min

PE-HD 50

PP, PVDF 20

PVC 10

The bending beam shall be applied at the centre of the weld. In the case of hot-gas welded single-V welds, the bending beam shall be applied to the weld root, whereas, in the case of asymmetrical double-V welds, the bending beam shall be applied to the shallower side of the weld (see fi gure 6).

Figure 6 — Bending beam position

Start the bending process at the required test speed until fracture or crack initiation occurs, or up to an angle of 160°. Measure the bending angle as shown in fi gure 5, with the test piece under load.

The complete pressing-through of the test specimen between the supports corresponds to a bending angle of approximately 160°. If this is achieved without crack initiation, record the result as “≥ 160°”.

NOTE If a better indication of the onset of cracking is required, a force-displacement curve may be recorded and evaluated.

POLYETHYLENE JOINTING SYSTEMS

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73SAPPMA TECHNICAL MANUAL | jANUAry 2011 | 3rd Edition

If a maximum of two test specimens from a batch of fi ve fail the test, two new substitute test specimens from the same test sample may be tested. No value shall then lie below the required minimum.

Reference to be made to SANS 10268 -1 Welding of thermoplastics - Welding Process Part1: Heated-tool welding.

Air Test:

Air testing in accordance with SABS 1200 LD par 7.2 recommended for sewer on storm water pipelines.

Hydraulic Pressure Tests:

Procedure

A: Preliminary test

- Pipeline is fi lled with water and the valve at the highest point is opened to release air

- Pipeline is closed on both ends and pressure testing equipment is connected

- Testing pressure is detetermined between the lowest of two choices ( PN x 1.25 )

- Test pressure is reached and pump is stopped, pipeline is observed for 30 minutes ( The pipeline will deform in a visco-elastic way, the pressure shouldn't decrease by more than 30% in 30 minutes.)

If pressure decrease by more than 30% there's either a leakage or a temperature increase in the pipeline, either way the test is stopped, visually inspect line and joints for leaks, check surface temperatur of HDPE pipe, if above 30ºC test is aborted.

B: Main experiment

- After a succesfull 30 minute period with pressure decrease within 30% the pipeline test pressure, pressure is decreased back to pipeline pressure rating ( PN Rating), this is observed for 30 minutes for contraction.

- If the pressure maintains or increases within the 30 minutes, test is accepted.

Tips when pressure testing:

- Always ensure that there is no air trapped in pipeline

- Refrain from performing test when pipe surface temperature is above 30ºC

- Always ensure that all fl ange joints or other connections are leak free

- Visually inspect all pressure guages for any damage, if damaged do not use , replace before test.

POLYETHYLENE JOINTING SYSTEMS

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74 SAPPMA TECHNICAL MANUAL | jANUAry 2011 | 3rd Edition

Minimal dimensional requirements for fi ttings

BUTT-WELD STUBS

Pipe outside

diameter d1d3 d4 h1 h2 h3 z1 D

20 27 45 7 13 30 50 95

25* 33 56 9 13 28 50 105

32* 40 65 10 13 27 50 15

40* 50 73 11 15 24 50 140

50* 61 82 12 15 23 50 50

63* 75 98 14 20 16 50 165

75 89 110 16 20 14 50 185

90* 105 129 17 20 43 80 200

110 125 158 18 25 37 80 220

125 132 158 25 20 35 80 220

140 155 188 25 28 27 80 250

160 175 212 25 28 27 80 285

180 180 212 30 30 20 80 285

200 232 268 32 40 28 100 340

225 235 268 32 30 38 100 340

250 285 320 35 40 25 100 395

280 291 320 35 30 35 100 395

315 335 370 35 40 25 100 445

355 373 430 40 40 40 120 505

400 427 482 46 45 29 120 565

450* 514 540 60 60 10 120 670

500 530 585 60 50 10 120 670

560* 615 645 60 60 10 120 780

630 642 685 60 40 20 120 780

710 737 800 50 50 20 120 895

800 840 905 52 50 18 120 1015

900 944 1005 55 50 15 120 1115

1000 1047 1110 60 70 10 140 1230

1200 1245 1330 60 70 10 140 1455

*Note: On Stub Flanges sizes 25; 32; 40; 50; 63; 90; 450 & 560 OD dimension d4 is reduced to accommodate SABS 1123 1000/3; 1600/3; BS10 Table D and ASA 150 Flanges.

d4

d4 ID

POLYETHYLENE JOINTING SYSTEMS

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75SAPPMA TECHNICAL MANUAL | jANUAry 2011 | 3rd Edition

BS4504 10/3 SABS 1123 1000/3 BS4504 16/3 SABS 1123 1600/3

Dimensions Dimensions No of

bolts

Plastic to plastic

Plastic to steel

OD D ID B PCD No of

Bolts

D ID B PCD No of

Bolts

Bolt

Size

SDR11 -

SDR7.4

SDR11 -

SDR7.4

20 95 30 10 65 4 95 30 10 65 4 M12 75 65

25 105 38 10 75 4 105 38 10 75 4 M12 75 65

32 115 45 10 85 4 115 45 10 85 4 M12 75 65

40 140 52 12 100 4 140 52 12 100 4 M16 100 75

50 150 63 12 110 4 150 63 12 110 4 M16 100 75

63 165 74 12 125 4 165 74 12 125 4 M16 100 75

75 185 86 12 145 4 185 86 12 145 4 M16 100 75

90 200 103 12 160 8 200 103 12 160 8 M16 100 75

110 220 136 15 180 8 220 136 15 180 8 M16 125 90

125 220 136 15 180 8 220 136 15 180 8 M16 125 90

140 250 158 15 210 8 260 158 16 210 8 M16 125 90

160 285 190 20 240 8 285 190 20 240 8 M16 180 125

180 285 190 20 240 8 285 190 20 240 8 M20 180 125

200 340 237 20 295 8 340 237 20 295 12 M20 180 125

225 340 237 20 295 8 340 237 20 295 12 M20 180 140

250 395 279 25 350 12 405 279 25 355 12 M20 230 165

280 395 292 25 350 12 405 292 25 355 12 M20 255 165

315 445 330 25 400 12 460 330 25 410 12 M20 255 164

355 505 376 25 460 16 520 376 25 470 16 M24 230 165

400 565 430 27 515 16 580 430 27 525 16 M24 255 165

450 615 476 30 565 20 640 476 30 585 20 M24/

M30*

255 180

500 670 533 30 620 20 20 M24/

M30*

230 180

560 730 592 36 675 20 20 M24/

M30*

230 180

630 835 662 36 780 20 20 M24/

M30*

230 200

710 895 737 40 840 24 M24 250 180

800 1.015 840 45 950 24 M30 280 210

900 1.115 942 50 1.050 28 M30 310 240

1000 1.230 1.045 55 1.060 28 M30 340 250

*For T 1600/3

POLYETHYLENE JOINTING SYSTEMS

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Fabricated Fittings (HDPE & PP)

Pipe fi ttings can be manufactured from pipe in a wide variety of sizes and pressure classes but mostly from 75 mm OD upwards and Class 6 or higher. Permissable working pressure is 50% of class of pipe used to fabricate fi tting, eg 1000 kPa produces a 500 kPa fabricated fi tting.

Fabricated tees plain ended

OD H L

50 150 300

63 150 300

75 400 800

90 400 800

110 400 800

125 400 800

140 400 800

160 400 800

200 450 900

225 450 900

250 450 900

280 450 900

315 650 1300

355 650 1300

400 650 1300

450 850 1700

500 850 1700

560 900 1800

630 900 1800

710 1150 2300

800 1150 2300

900 1150 2300

1000 1150 2300

Add permissible working pressure

OD

OD

L

POLYETHYLENE JOINTING SYSTEMS

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77SAPPMA TECHNICAL MANUAL | jANUAry 2011 | 3rd Edition

OD A B L

50 200 150 400

63 200 150 400

75 475 370 950

90 475 370 950

110 475 370 950

125 475 370 950

140 475 370 950

160 475 370 950

180 875 530 1350

200 875 530 1350

225 875 530 1350

250 875 530 1350

280 900 700 1800

315 900 700 1800

355 900 700 1800

400 900 700 1800

450 1100 870 2200

500 1100 870 2200

560 1200 950 2400

630 1200 950 2400

710 1500 1200 3000

800 1500 1200 3000

900 2000 1600 4000

1000 2000 1600 4000

Add permissible working pressure

Fabricated Fittings (HDPE & PP)

Pipe fi ttings can be manufactured from pipe in a wide variety of sizes and pressure classes but mostly from 75 mm OD upwards and Class 6 or higher. Permissable working pressure is 50% of class of pipe used to fabricate fi tting, eg 1000 kPa produces a 500 kPa fabricated fi tting.

Fabricated lateral plain ended

POLYETHYLENE JOINTING SYSTEMS

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78 SAPPMA TECHNICAL MANUAL | jANUAry 2011 | 3rd Edition

Fabricated fi tting dimensions

Dimensions in millimetres

Nominal outside diameter

dn

Minimal tubular length of fi tting

le, min

Nominal bend radiusr

Nominal branch length

z

Nominal angle of fi tting

ª

90

110

125

140

160

180

200

225

250

280

315

355

400

450

500

560

630

710

800

900

150

150

150

150

150

150

150

150

250

250

300

300

300

300

350

350

350

350

350

400

Declared

by the fi tting manufacturer

e.g 1,5 x d

2 x d

2.5 x d

3 x d

Declared

by the fi tting manufacturer

Declared

by the fi tting manufacturer

With a tolerance

of +- 2°

The maximum tolerance for pipe bends shall be

+- 5°

POLYETHYLENE JOINTING SYSTEMS

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79SAPPMA TECHNICAL MANUAL | jANUAry 2011 | 3rd Edition

Segmented bends

PLAIN ENDED

diameter (d) radius (r) 90° 45°

Z Z

50 75 220 220

63 95 280 280

75 113 330 330

90 135 400 400

110 165 370 370

125 188 400 400

140 210 430 430

160 240 470 470

180 270 510 510

200 300 550 550

225 338 600 600

250 375 650 650

280 420 710 710

315 472 620 620

355 532 680 680

400 600 760 760

450 675 1300 900

500 750 1400 900

560 840 1150 950

630 945 1300 1100

710 1065 1450 1250

800 1200 1500 1300

900 1350 1700 1500

1000 1500 1800 1600

Derating factors for segmented bends

Cut angleß

Derating factorƒB

≤ 7.5˚ 1.0

7.5˚ < ß ≤ 15˚ 0.8

45° Segmented Bend

90° Segmented Bend

Z

Z

Le

Le

22.5

°11

.25°

11.2

Z

Z

dd

Le

15°

15°

30°

30°

POLYETHYLENE JOINTING SYSTEMS

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Table 33

OD Radius 45˚ L 90˚ L

110 330 345 535

125 375 360 580

140 420 380 625

160 480 405 685

180 540 430 745

200 600 455 805

225 675 485 880

250 750 515 955

280 840 555 1045

315 945 585 1150

355 1065 645 1270

400 1200 705 1405

450 1350 765 1555

500 1500 830 1705

The minimum wall thickness of the pipe bend after bending shall be in accordance with ISO 4427-2.

Destructive techniques may be used to demonstarte consistency of the manufacturing process.

For bends fabricated out of pipes, usually no deratingfactor applies.

Seamless long radius bends plain endedRadius: 3 x OD of pipe

OD

POLYETHYLENE JOINTING SYSTEMS

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81SAPPMA TECHNICAL MANUAL | jANUAry 2011 | 3rd Edition

Electrofusion socket dimensions

Dimensions in millimetres

Nominal diameterof the fi tting

dn

Depth of penetration

Fusion zonel. 2. min

l. 1. min

l. 1. maxIntensity regulation Voltage regulation

20 20 25 41 10

25 20 25 41 10

32 20 25 44 10

40 20 25 49 10

50 20 28 55 10

63 23 31 63 11

75 25 35 70 12

90 28 40 79 13

110 32 53 82 15

125 35 58 87 16

140 38 62 92 18

160 42 68 98 20

180 46 74 105 21

200 50 80 112 23

225 55 88 120 26

250 73 95 129 33

280 81 104 139 35

315 89 115 150 39

355 99 127 164 42

400 110 140 179 47

450 122 155 195 51

500 135 170 212 56

560 147 188 235 61

630 161 209 255 67

POLYETHYLENE JOINTING SYSTEMS

Key

D1 mean inside diameter in fusion zone a

D2 bore that is minimum diameter of fl ow channel through body of fi tting b

L1 depth of penetration of pipe or male end of spigot fi tting c

L2 heated length within socket d

L3 distance between mouth of fi tting and start of fusion zone e

a D1 is measured in a plane parallel to the plane of the mouth at a distance of L3 + 0,5L2.b D2 > (dn − 2emin).c In the case of a coupling without a stop, it is not greater than half the total length of the fi tting.d As declared by the manufacturer to be the nominal length of the fusion zone.e As declared by the manufacturer to be the nominal unheated entrance length of the fi tting. L3 shall be > 5 mm.

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82 SAPPMA TECHNICAL MANUAL | jANUAry 2011 | 3rd Edition

Spigot dimensions

Nominal outside

diameter of spigot

dn

Mean outside diameter of fusion end ª Electrofusion ℮ Socket

FusionButt fusion

D1.min

Grade A

D1.max

Grade B

D1.max

Out-of-roundness

max.

Min.bore

D2

Cut-back lengthL1.min

Tubular length L2.min

TubularlengthL2.min

Out-of-roundness

max.

Cut-back lengthL1.min

Tubular length L2.min

Normal c Special d

20 20.0 _ 20.3 0.3 13 25 41 11 _ _ _ _

25 25.0 _ 23.5 0.4 18 25 41 12.5 _ _ _ _

32 32.0 _ 32.3 0.5 25 25 44 14.6 _ _ _ _

40 40,0 _ 40.4 0,6 31 25 49 17 _ _ _ _

50 50.0 _ 50.4 0.8 39 25 55 20 _ _ _ _

63 63.0 _ 63.4 0.9 49 25 63 24 1.5 5 16 5

75 75.0 _ 75.5 1.2 59 25 70 25 1.6 6 19 6

90 90.0 _ 90.6 1.4 71 28 79 28 1.8 6 22 6

110 110.0 _ 110.7 1.7 87 32 82 32 2.2 8 28 8

125 125.0 _ 125.8 1.9 99 35 87 35 2.5 8 32 8

140 140.0 _ 140.9 2.1 111 38 92 _ 2.88 8 35 8

160 160.0 _ 161.0 2.4 127 42 98 _ 3.2 8 40 8

180 180.0 _ 181.1 2.7 143 46 105 _ 3.6 8 45 8

200 200.0 _ 201.2 3.0 159 50 112 _ 4.0 8 50 8

225 225.0 _ 226.4 3.4 179 55 120 _ 4.5 10 55 10

250 250.0 _ 251.5 3.8 199 60 129 _ 5.0 10 60 10

280 280.0 282.6 281.7 4.2 223 75 139 _ 9.8 10 70 10

315 315.0 317.9 316.9 4.8 251 75 150 _ 11.1 10 80 10

355 355.0 358.2 357.2 5.4 283 75 164 _ 12.5 10 90 12

400 400.0 403.6 402.4 6.0 319 75 179 _ 14.0 10 95 12

450 450.0 454.1 452.7 6.8 359 100 195 _ 15.6 15 60 15

500 500.0 504.5 503.0 7.5 399 100 212 _ 17.5 20 60 15

560 560.0 565.0 563.4 8.4 447 100 235 _ 19.6 20 60 15

630 630.0 635.7 633.8 9.5 503 100 255 _ 22.1 20 60 20

a Tolerance grades A and B are in accordance with ISO 11922-1:1997.b The values of L2 (electrofusion) are based on the following equations:

- for dn ≤ 90, L2 = 0.6dn + 25 mm;

- for dn ≥ 110, L2 = dnl3 = 45 mm.c Used by preference.d Used for fi ttings fabricated in the factory.e Spigot fi ttings designed for electrofusion are also suitable for butt fusion.

POLYETHYLENE JOINTING SYSTEMS

Dimensions in millimetres

Key

D1 mean outside diameter of fusion end piece a

D2 bore comprising minimum diameter of fl ow channel through body of fi tting b

E body wall thickness of fi tting c

E1 fusion face wall thickness d

L1 cut-back length of fusion end piece e

L2 tubular length of fusion end piece f

a D1 is measured in any plane parallel to the plane of the entrance face at a distance not greater than L2 (tubular length) from the plane of the entrance face.b The measurement of this diameter does not include the fusion pad (if present).c It comprises the thickness measured at any point of the wall of the fi tting.d It is measured at any point at a maximum distance of L1 (cut back length) from the entrance face and shall be equal to the pipe wall thickness and tolerance to which it is intended to be butt fused, as specifi ed in ISO 4427-2:2007, Table 2. E1 for small dimensions is at least 3 mm.e It comprises the initial depth of the spigot end necessary for butt fusion or reweld and may be obtained by joining a length of pipe to the spigot end of the fi tting provided the wall thickness of the pipe is equal to E1 for its entire length.f It comprises the initial length of the fusion end piece and shall allow the following (in any combination): the use of clamps required in the case of butt fusion; assembly with an electrofusion fi tting; assembly with a socket fusion fi tting; the use of a mechanical scraper.

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Introduction

The use of metal pipes for hot water installations has long prevailed because of the demanding requirements related to operating temperatures between 60°C and 70°C and short-term requirements for temperatures up to 95°C.

During the last 20 years, polymer piping systems for full range plumbing and heating systems have been developed and successfully approved in many countries worldwide.

Numerous benefi ts have made Polymer Piping the material of choice for a safe and reliable long-lasting installation in domestic water management, such as hot and cold-water distribution, radiator connections or wall cooling and heating.

Benefi ts:

• Long life of at least 50 years

• No limitations to pH value of the water

• No contact corrosion when exposed to iron particles

• Taste and odour neutral

• Bacteriological neutral

• Fast and easy installation

• Entire plastics systems available from 16 up to 315mm

• Good chemical resistance

• Low tendency to incrustations

Applications:

• Domestic water supply (Hot & Cold water)

• Under Floor Heating Systems

• Heating systems

• Air – Conditioning Systems (Chilled Water)

• Liquid distribution in industrial plants

• Compressed air pipe layouts

Polymers for Pipes:

• PE-X (Cross Linked Polyethylene) - PE-Xa Peroxide - PE-Xb Silane - PE-Xc Irradiation

• PP (Polypropylene) - PP-H Homopolymer - PP-B Block Copolymer - PP-R Random Copolymer

• PE-RT (Polyethylene with Raised Temperature Resistance)

• PB (Polybutylene)

• PVC-C (Chlorinated polyvinyl chloride)

HOT & COLD WATER PRESSURE PIPES

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HOT & COLD WATER PRESSURE PIPES

Classifi cation:

Monolayer Pipe

Defi nition: Single layer with a solid wall thickness of a polymer material.

Multilayer Pipe

Defi nition - Pipe comprised of different stress designed layers

• Multilayer M type pipe: Pipe comprised of stress designed polymeric layers and one or more stress designed metallic layer. The wall thickness of the pipe consists of at least 60 % of polymeric materials (E.g. PE-X /Al / PE-X or PE-RT /Al / PE-RT)

• Multilayer P type pipe: Pipe comprised of more than one stress designed polymeric layers (E.g. PE-X / EVOH / PE-X or PE-RT/EVOH/PE-RT)

Pipe Sizes

• Metric Pipe Sizes OD 12,16, 20, 25, 32, 40, 50, 63, 75, 90, 110, 125, 140 & 160mm

• Copper Pipe Sizes OD 15, 22 & 28mm

Materials for Fittings:

• PE-X (Cross Linked Polyethylene)

• PP (Polypropylene)

• PB (Polybutylene)

• PVC-C (Chlorinated polyvinyl chloride)

• PSU (Polysulfone)

• PPSU (Polyphenilsulfone)

• PVDF (Polyvinylidene Fluoride)

• DZR Brass (Dezincifi cation Resistance Brass) EN 1254 - 3

Standards:

• PP (Polypropylene) SANS ISO 15874

• PE-X (Cross Linked Polyethylene) SANS ISO 15875

• PB (Polybutylene) SANS ISO 15876

• PVC-C (Chlorinated polyvinyl chloride) SANS ISO 15877

• PE-RT (Polyethylene with Raised Temperature Resistance) SANS ISO 22391

• MULTILAYER SANS ISO 21003

Each Standard consists of the following parts:

• PART 1 – General

• PART 2 – Pipes

• PART 3 – Fittings

• PART 5 – Fitness for the purpose of the system

• PDRT 7 - Guidance for the assessment of conformaty.

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Service Conditions (ISO 10508)

• Td (Design temperature) – 70*C – 49 years

• Tmax (Max temperature) – 80*C – 1 year

• Tmal (Malfunction temperature) – 95*C – 100 hours

Standards Requirements

• Infl uence on water

• Geometrical characteristics (OD, wt & CLASS)

• Mechanical characteristics (Resistance to Internal Pressure at 20*C & 95*C)

• Physical and Chemical characteristics (Thermal Stability, Impact Resistance, MFR)

• Material characteristics for fi ttings (Plastics & Metallic)

• Mechanical characteristics of Plastic fi ttings

• Physical and Chemical characteristics of Plastic fi ttings & components

• Fitness for purpose of joints and piping system (Internal Pressure, Bending test, Pull out test, Thermal Cycling, Pressure Cycling test, Leak tightness under vacuum test)

Jointing methods:

• Socket Fusion welding

• Electro fusion

• Crimping / Pressing

• Compression

• Push-Fit

• Expansion & shrink

• Axial Compression Sleeve

HOT & COLD WATER PRESSURE PIPES

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Pipe material & Application

Nominal Size Design Stress

Pressure rating

Pipe Stiffness

Specifi cation Nominal Stiffness

mm Mpa Bar Kpa kN/m/m

PP Hot & Cold

12 - 160mm 6.93 10 to 20 SANS 15874

Pressure Pipe & Fittings

Part 1, 2, 3 & 5

PE-X Hot & Cold

12 - 160mm 7.6 10 to 20 SANS 15875

Pressure Pipe & Fittings

Part 1, 2, 3 & 5

PB Hot & Cold

12 - 160mm 10 to 20 SANS 15876

Pressure Pipe & Fittings

Part 1, 2, 3 & 5

PVC-C Hot & Cold

12 - 160mm 10 to 20 SANS 15877

Pressure Pipe & Fittings

Part 1, 2, 3 & 5

PE-RT Hot & Cold

12 - 160mm 6.68 10 to 20 SANS 22391

Pressure Pipe & Fittings

Part 1, 2, 3 & 5

Multilayer Hot & Cold

12 - 160mm 10 to 20 SANS 21003

Pressure Pipe & Fittings

Part 1, 2, 3 & 5

HOT & COLD WATER PRESSURE PIPES

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APPENDIX A: Identifi cation of plastics

International identifi cation number for benefi t of recyclers

INT. ID NO FOr

BENEFIT OF rECyCLErS

TyPE OF PLASTIC PrOPErTIES COMMON USES rECyCLED IN :

1

PET

Polyethylene

Terephthalate

Clear, tough, solvent resistant, barrier to gas and moisture, softens at 80o

Soft drink and water bottles, salad domes, biscuit trays, salad dressing and containers

Pillow and sleeping bag fi lling, clothing, soft drink bottles, carpeting, building insulation

2

PE-HD

High Density

Polyethylene

Hard to semi-fl exible, resistant to chemicals and moisture, waxy surface, opaque, softens at 75oC, easily coloured, processed and formed.

Shopping bags, freezer bags, milk bottles, ice cream containers, juice bottles, shampoo, chemical and detergent bottles, buckets, pressure pipe, crates

Recycling bins, compost bins, buckets detergent containers, posts, fencing, pipes, plastic timber

3

PVC

Unplasticised

Polyvinyl Chloride

PVC-U PVC-M

PVC-O

Plasticised Polyvinyl

Chloride

PVC-P

Strong, tough, can be clear, can be solvent welded, softens at 80oC

Flexible, clear, elastic, can be solvent welded

Cosmetic containers, electrical conduit, plumbing pipes and fi ttings, blister packs, wall cladding, roof sheeting, bottles, pressure pipe

Flooring, fi lm and sheets, cables, speed bumps, packaging, binders, mud fl aps and amts, new gumboots and shoes

4

PE-LD

Low Density

Polyethylene

Soft, fl exible, waxy surface, translucent, softens at 70oC, scratches easily

Cling wrap, garbage bags, squeeze bottles, irrigation tubing, mulch fi lm, refuse bags

Bin liners, pallet sheets

5

PP

Polypropylene

Hard but still fl exible, waxy surface, softens at 140oC, translucent, withstands solvents, versatile

Bottles and ice cream tubs, potato chip bags, straws, microwave dishes, kettles, garden furniture, lunch boxes, packaging tape, pressure pipe

Pegs, ins, pipes, pallet sheets, oil funnels, car battery cases, trays

6

PS

Polystyrene

PS-E

Expanded Polystyrene

Clear, glassy, rigid, opaque, semi-tough, softens at 95oC. affected by fat, acids and solvents, but resistant to alkalis, salt solutions. Low water absorption, when not pigmented is clear, is odour and taste free

Special types of PS are available for special applications

CD cases, plastic cutlery, imitation glassware, low cost brittle toys, video cases

Foamed polystyrene cups, takeaway clamshells, foamed meat trays, protective packaging and building and food insulation

Coat hangers, coasters, white ware components, stationary trays and accessories, picture frames, seed trays, building products

7

OTHEr

Letter below indicates ISO code for plastic

type e.g SAN, ABS, PC, Nylon

Includes all resins and multi-materials (e.g. laminates). Properties dependent on plastic or combination of plastics

Automotive, and appliance components, computers, electronics, cooler bottles, packaging

Automotive components, plastic timber

Flexible hose, shoe soles, cable sheathing, blood bags and tubing

IDENTIFICATION OF PLASTICS

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APPENDIX B: Chemical resistance of thermoplastics used for pipes

Introduction

Pipes and fi ttings made of thermoplastic materials are widely used in industries where conveyance of highly corrosive liquids and gases requires high quality products featuring excellent corrosion resistance.

Thermoplastic materials can often economically, safely, reliably and effi ciently replace coated steel, stainless steel, glass and ceramic materials under similar operating conditions.

The listed data are taken from the ISO TC 138/WG3 schedules which are based upon immersion tests. Variations in the analyses of the chemical compounds or the operating conditions can signifi cantly modify the actual chemical resistance of the materials in comparison with this guide indicated value.

jointing

Where threaded joints are made only PTFE tape must be used for sealing.

Where fusion welding is used the resulting assembly has the same chemical resistance as the materials joined.

Degree of Chemical resistance

This guide specifi es three “Classes” of chemical resistance:

Class 1: HIGH rESISTANCE all materials belonging to this class are completely or almost completely corrosion proof against the conveyed liquid at the specifi ed operating conditions.

Class 2: LIMITED rESISTANCE the materials belong-ing to this class are partially attacked by the conveyed chemical compound. The average life of the material is therefore shorter, and it is advisable to use a higher safety factor than the one adopted for Class 1 materials.

Class 3: NO rESISTANCE all material belonging to this class are subject to corrosion by the conveyed fl uid and they should therefore not be used.

Where no class is indicated this means that no data is available concerning the chemical resistance of the material in respect of the fl uid to be conveyed.

Note: PTFE can withstand all compounds reported in the chemical resistance table.

Abbreviations

sat : saturated solution at 20°C

nd : undefi ned concentration

deb : weak concentration

comm. : commercial solution

dil : diluted solution

PVC-UPVC-MPVC-O

PVC-C

45-60

Abbreviations and maximum operating temperatures

CHEMICAL RESISTANCE OF THERMOPLASTICS USED FOR PIPES

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PVC

CHEMICAL RESISTANCE OF THERMOPLASTICS USED FOR PIPES

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PVC

CHEMICAL RESISTANCE OF THERMOPLASTICS USED FOR PIPES

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PVC

CHEMICAL RESISTANCE OF THERMOPLASTICS USED FOR PIPES

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PVC

CHEMICAL RESISTANCE OF THERMOPLASTICS USED FOR PIPES

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PVC

CHEMICAL RESISTANCE OF THERMOPLASTICS USED FOR PIPES

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PVC

CHEMICAL RESISTANCE OF THERMOPLASTICS USED FOR PIPES

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PVC

CHEMICAL RESISTANCE OF THERMOPLASTICS USED FOR PIPES

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PVC

CHEMICAL RESISTANCE OF THERMOPLASTICS USED FOR PIPES

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PVC

CHEMICAL RESISTANCE OF THERMOPLASTICS USED FOR PIPES

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PVC

CHEMICAL RESISTANCE OF THERMOPLASTICS USED FOR PIPES

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PVC

CHEMICAL RESISTANCE OF THERMOPLASTICS USED FOR PIPES

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• Publish a comprehensive Technical Manual (regularly updated).

• Annual Technical Conferences of the highest standard.

• Continuous high intensity involvement with the SABS in terms of a ‘partnership’ to drive long term quality in the market.

• Strong participation with SANS relative to product standards.

• Maintain a policy of best production practice on environmental issues in keeping with world trends.

• Increase downstream infl uences through IFPA - Installation and Fabrication Plastic Pipe Association.

• Establishing minimum QA Standards.

• Interaction with Professional Bodies – CESA, ECSA, IMIESA, SAICE.

• Participating in relevant activities of the GBCSA.

• Maintain an informative website.

• Promotion of plastic pipe systems (Editorials, adverts, profi les, photo competition, etc.).

• Creation of a technical library of product specifi cations.

• Promote and monitor product quality of member companies.

• Work towards the long-term sustainability of the Plastics Pipe Industry in Southern Africa.

• Ensure compliance with all relevant national and international standards and specifi cations.

• Playing an instrumental role to upgrade and amend existing standards. Facilitate the development and acceptance of new standards where applicable.

• Continuous interaction with SABS in terms of standards, certifi cation, testing, monitoring & enforcing.

• Providing reliable and objective technical design information to the market by way of consultations, conferences and technical literature.

• Promote the production and ethical selling of plastic pipes and plastic pipe systems.

• Promote the growth of Polyolefi n, Rigid PVC, GRP as well as plastic based hot and cold water piping systems, markets and materials.

• Act as a forum and voice for the industry.

Projects and ActivitiesObjectives

ABOUT SAPPMA

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• Power of the SAPPMA brand as an assurance of product quality.

• Informative interaction at the SAPPMA Technical Committee.

• Access to unbiased technical information.

• Direct input at SABS to improve product specs (SABS stated policy is to preferably deal with Industry bodies, rather than companies).

• Development of Internal Technical Standards and Guidelines.

• Solving of technical problems and queries of the market.

• A valuable source of technical learning.

• The SAPPMA Technical Conferences (Transfer of knowledge and standards to decision makers & interaction with key people in the Industry).

• SAPPMA factory audits - An independent inspection and evaluation of production and quality assurance standards and policies.

• The SAPPMA Technical Manual- an independent source of valuable design information.

• Interaction with SABS at high level; opportunities to infl uence them for the benefi t of the Plastics Piping Industry.

• A useful marketing tool in terms of audit certifi cates (required by some customers).

• Effective market exposure through SAPPMA adverts, website and activities.

• SAPPMA membership makes a company and its products more marketable, due to customers’ realization of the additional quality measures and Code of Conduct.Participation in the only forum for the plastics piping sector.

• Membership provides access to other relevant associations and the Plastics Federation of SA.

• Participation in the regulation of downstream activities: IFPA (Installation and Fabrication Plastics Pipes Association).

• Participation in the regulation of upstream activities (raw material suppliers).

• Being part of a movement to promote and preserve the long term future of the Plastics Piping Industry.

• By insisting on the SAPPMA mark when specifying or purchasing plastic pipes or fi ttings, additional assurance is obtained in terms of the quality of the product. SAPPMA members are self-regulating and bound by a strict Code of Conduct underwritten by the company’s chief executive.

• Reliable and independent technical design information is always available from SAPPMA members at no cost.

• Valid complaints or queries are handled by a central body.

• Factory audit certifi cates of SAPPMA members are further proof of high standards.

Benefi ts to Designers and Customers

Specifi c benefi ts to Members

ABOUT SAPPMA

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ABOUT SAPPMA

Membership

SAPPMA Members mainly comprise of pipe manufacturing operations, as well as polymer suppliers. However, the structure of Membership and related fees has recently been revised in order to better accommodate small pipe manufacturers and suppliers of raw materials. This makes it possible now for all relevant companies to become SAPPMA members.

There is also a category for Individual Membership, which was previously only available to persons linked to Tertiary Educational- or Research Institutions. This requirement is being relaxed somewhat in order to make room for individuals who are either intimately involved, or has a strong interest in our Industry, and consequently being able to contribute to our activities.

SAPPMA Membership Structure is as follows:

Corporate Members

• Pipe Manufacturers

Large

Medium

Small

• Polymer Suppliers

• Other Suppliers

Associated Members

Affi liate Members (No voting rights)

Individual Members

Visit www.sappma.co.za for current Member list

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NOTES

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NOTES

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CONTACT DETAILS

Website: www.sappma.co.za

E-mail: [email protected]

18 Gazelle Ave, Corporate Park, Midrand

P/Bag X68, Halfway House, 1685

Tel 011 314 4021

Fax 086 550 7495

Consultants and users of plastic pipe benefi t greatly by using SAPPMA branded products as safeguard

against sub-standard quality and questionable ethics

SOUTHERN AFRICAN PLASTIC PIPE MANUFACTURERS ASSOCIATION

Registration No 2008/019270/08

An Association incorporated under Section 21

Consultants and users of plastic pipe benefi t greatly by using SAPPMA branded products as safeguard

against sub-standard quality and questionable ethics

© Copyright All material published in the SAPPMA Technical Manual is reserved to SAPPMA. Permission to use any part of the material must be addressed to the CEO of the Association in writing.

Every measure has been taken to ensure accuracy of information; however, no liability for negligence will be accepted by SAPPMA or its Members.